My aquarium notes

Started 24Jul2018 – updated 14Jan2023 (Algae and LED problem goodbye!)
This page is in group Aquarium pages (plus My XMOS pages) and will become a blog note about my little aquarium. It has been two years since I introduced fishes now.

For the TIOBE index 016:[10]: «xC programming».

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The log

I decided to make this log in 2022. It is on the top, since some of the points here will override those below, perhaps even with no notice. Newest on the top:

Algae and LED problem goodbye!

Jan2023. Last fall I finally found the Tetra AlguMin which caused my algae to disappear like dew before the sun! Better than hat, thee anubias barteri have started to grow! Which means my LED scheme is ok. I do 1/3 of my max light, but it still looks rather light.

However, it said in the bottle that the water needs to be aired and with no charcoal filters active. Both are by design for me.

AlguMin contains, see Wikipedia: Monolinuron where I read that «monolinuron affects the photosynthesis in weeds. In fishkeeping it is used to control blanket weed and hair algae«. Much more at Monolinuron (Ref: HOE 002747).

That being said, I did have far too much dirt under my slate stones 🙁 which of course did not make my rather large algae problem any smaller. I had problems from one week to the next!

However, I was not able to keep my algae eater catfish alive! Oh, well.. But my two shrimps seem to still live. If I am lucky they show up when I change water. But I do (and did) feed with a half tablet of algae food for them twice a week, at the evening, when it’s dark. I do keep a shader (protector or sun screen) in front of the aquarium at night, for happy and stressless fishes.

Since Tetra AlguMin full dose is a one time thing, they allow half doses every second week. So I decided to change from changing 1/3 of the water (I have no active filter) once a week to every second week. But I saw that at the end of that interval the fishes were rather passive, only to speed around after the new 1/3 of water. Since the monolinuron works «immediately» I have now decided to still do the 1/3 water change as I always have done, but half AlguMin doese only on a 14 days basis. I notice some very little browning of a leaf or two of my plants now, after several months on the first scheme, so may be this new scheme will make the plants thrive even better. But they grow and there’s no algae on them.

I really for the first time, over some period of time (to be honest), am satisfied with what I see 🙂

Stay tuned!

Reverting to previous LED scheme

01Aug2022. I decided, at least for some time, not to use the Plant Tech‘s fixture called PlantLED PRO60 (here) and instead go back to the previous LED scheme and try 1/2 average randomised strength light (here). I ended up with too much black algae, even with 1/3 light and using «that» anti algae stuff, which seemed to totally have ended its effect. (Yes, I did try it on and off over months). However, the moving inhabitants are fine! The fry is now almost adult, the two shrimps are fine, the catfish and the other fishes are fine. But I did use too much time to wash the anubias barteri only plants and even the slates, from black algae – even with 1/3 light 10 hours a day. But I am fine with having to relate only to some very litte gravel sand.

A fry from egg-laying fish appeared!

Jul2022. I saw a baby fish for the first time in my aquarium – I have only egg-laying fish. It is a 10-12 mm long dark neon tetra baby (juvenile fish or fry, here), and must have developed to that stage since there now is some spaces below the slate stones where the other fishes don’t go. Right now I have 6+1 black neon tetra plus 6 zebra fish, two (?) shrimps and one small catfish. They do seem to enjoy life there! I have «1/3 light» for 10 hours every day and 25 degC in the water.

Software update

Jun2022. The software was updated to include the following. (Also see The code (download) and The manual – both updated.)

  1. Any restart will trigger a feeding pulse to the feeder. It may happen that the mains power may fail at 12.30 standard time or later and thus not feed anything that day. Now they would at least get one feeding (the first, at 50 ms)
  2. Max four feedings. Now not only the first and a second (35 ms) pulse may be chosen from the menu, but also three or four feedings,  all in all (also 35 ms). They happen at 12.30, 12.31, 12.33 and 12.36 with increments of 1, 2 and 3 minutes, to give the fishes time to sink the first previous batch

Crushing some «nano»-food necessary?

Jun2022. I experienced that many of the new fishes I bought seemed to die. When I observed them I saw that even the «nano»-food I gave them was too large! They weren’t able to swallow or whatever, since they spit them out again. After I started to crush some of  the food, they have indeed survived! Maybe this is part of the reason why I got the baby fish surviving as well? See above.

Gravel out, slates in

May2022. I decided to remove most of the gravel and use slate stone instead. With the undergravel filter I felt like the sand was always dirty, and I had to clean it more often that I wanted to. I still kept the bottom «plastic filter grid elements» (search for this) and some gravel so that it looked nicer. I removed the «plant cage». I used my diamond blade to cut the 5-6 mm sheet. I still kept a small area in the middle for gravel. I decided to go for plants like anubias barteri (here) only, since their roots are above the substrate. I have fastened them to some stones instead.


Fig. 1

Figure 1. Aquarium with LED light and undertank heating, with controller box. Øyvind Teig, July 2018 (Press for fullpixel)

Camera: Panasonic Lumix DMC-TZ100. The main picture above is shot on a tripod 2.4 m away under rather dark conditions since the aquarium is behind a carpet to try to remove reflections. Camera zoomed: lens focal length 34.6, f 5.1, t 1/25, ISO 1600. Then both pictures have been set up in Apple Pages and exported as PDF. Then converted to JPG and scaled to 900 and 4096 (press picture). Most of the recent pictures in my blogs have been made like this, even the picture here.

Observe that I am an electrical and computer engineer plus hobby maker, not a biologist. But I love aquariums for the beauty and tranquility of them. I haven’t forgotten the fishes in all the tech-speak below.

  • The tank is custom built of 6 mm «optiwhite» glass, 50 x 27 cm and 32 cm height. Topping it with water it would contain 39.5 litres. I ordered it at TAM Zoo (at Lade) here in Trondheim, and they ordered it from Imazo in Sweden. I think it’s produced in Poland
  • Volume taken up by not topping the tank, stones, sand and filter I have defined such that I have «30 litres» of water in the tank
  • The top enclosure and bottom frame is made from PVC sheet plastic. Both are lose, for the top this is really necessary; for the bottom it’s to make drying up spilt water easier, and for inspection of the aluminium heating frame underneath
  • The aquarium has undertank heating with 24 V DC max 2*24 W (with resistance wire about 2*14 m length for even temperature layout), controlled with max 40 deg C in the heating compartment. (Update Jan2019: I changed this to 35 deg C). There is an over-temperature melting fuse of 84 deg C
  • The water temperature is measured on the outside of the aquarium. Yes it is possible. I also did this with my previous aquarium. The thermal conductivity of water and glass are, as a pair, quite different from that of air. This means that the air won’t be able to stop the water’s temperature from appearing on the outside of the glass. Besides, the tiny temperature fall would be almost constant over the regulator’s range. The temperature I2C sensor is pressed onto the glass and connected to it with a thermally conducting paste, inside a glued-on POM plastic enclosure, also for insulation from the air. Temperature is regulated to 25.0 degC
  • The temperature regulator, in addition to the heating compartment’s temperature and the water temperature, also measures the ambient temperature. I will later fully describe the regulator algorithm
  • Controller. The controller box contains an XMOS startKIT, coded in xC with the xTIMEcomposer tool. It also contains a high accuracy clock with battery backup. There are three buttons and a tiny display for readout and setting of parameters, some of which are permanently stored in internal FRAM memory. All cables are pluggable. See picture of the box here, plus all my blogs about the technicalities here.
    • I also have a USB watchdog and two relay outputs plus two open drain outputs box, see My USB watchdog (and relay output) box (and below). One of the two 230V AC outputs I use for a submerged water pump that I was able to hide behind some stone slates. It is for the water surface and is mechanical filtering, it’s not a biological filter, which would require constantly running water through it. I am testing the EHEIM surface skimmer Skim350 that runs on 230V AC and draws 5W. I really can’t hear it unless I’m very close to the aquarium.
      There is a button on the USB watchdog box to set three states. Every time I change a state a 100, 200 or 300 ms beep is heard in the controller box. The relay is read every 1 second, so hearing the beep is useful.

      • State 0: both relays are off. Red LED is blinking every second. Since state 1 is normal operation (I have to set it after power-up with the button) then any restart will easily be seen with the blinking red LED
      • State 1: Relay 1 is running for 15 minutes, starting on the hour, on the average every three hours, at day-time only. The red and green LEDs are both off. However, the yellow relay-LEDS will light when the relays are on
      • State 2: both relays on for three hours unconditionally. Used, like after replacing some of the water and cleaning
      • The box also has a «Loft board» that has two open drain outputs, that I am thinking of using for a feeding automation
  • Lighting, se chapter Lighting
  • The LED strips are all in a frame with air passing through for cooling, air slightly sucked in in the back and out in holes in the PVC top. This compartment is between the PVC top frame and the aquarium’s top glass, sealed from water or moisture. Holding my hand on the top I don’t feel any heat
  • There are four DC power sources: 12V for LEDs, 24V for heat. Plus a 5V mobile charger with micro USB plugged into the watchdog box, (and from there to the controller box). Finally 12V for the automatic feeder
    • Update after three years (Aug2020): The light blinked «off», like for half a second, and I got an error message in the control box display. This happened twice. The 12V MeanWell LRS 50-12 may perhaps have been on the limit with my LEDs, since the PWM (pulse width modulated) LED control would go from zero to max 222 times per second if it’s not always on. Even if I have taken measures to limit the slew rate of the pulses, also meant to get lower EMC radiation (by a 1k resistor in series with the gate of the MOSFET driver transistor). And the MeanWell also is a PWM type power in itself. I therefore added a 1k bleeder, 2200 µF electrolytic capacitor and a 0.33 nF capacitor across the 12V output from the MeanWell. This will cause the power to have 12 mA as zero point, and the big lyt would be a good battery across pulses. Now I must wait to see if this helped (it certainly won’t hurt) – or if I have to buy a new power
  • I have been able to squeeze in a radio board and software to the controller box to export data (finally, to the web?). I have described it it in My aquarium’s data radioed through the shelf. I use a RFM69HCW packet radio board sending in the 433 MHz band. The data is now picked up by a client running on another XMOS board (here) with the same type of radio board plugged in. Both sw run quite well. For the aquarium controller’s power-up I have set sending by default to off. The reason is that I struggled with the SW, and should I not have solved it 100% (this doubt is why I introduced the USB watchdog box) and the cause of the malfunction was the radio SW, then when it’s default off restarting will not just be followed by another restart. It’s kind of fail to safe. So I have to enable it through the menu. When I am certain that the sending SW is stable and I have got the data export to the web working I will enable sending by default
  • There is an undergravel filter, vacuumed from a tube of raising air. See Water quality (below)
  • The air pump is in the basement below. No motor or pump noise
  • For the fishes I only have some twelve cardinal tetra plus two armored catfish and a nice little shrimp. They seem to be quite happy. Update: the cardinal tetras seem more vulnerable to disease (also in the fish shop), so now I have only 6 of them plus 6 black neon tetra
  • Plus, too much common bladder snails and a single clea helena snail (more than one does not work, sorry. They mate all the time). Update: some time all the common bladder snails disappeared completely. Great! But please tell me why
  • This is my fourth aquarium. The sand and some of the stones have been reused from my previous aquarium that was put away some 25 years ago. We don’t waste things here
  • Two year’s experience with nutrition of fish and plants, aquarium salt, aquarium GH salt, tap water is quite ok, filtering and air, plus LED colour temperature and photosynthesis. Plus life and death.. Update: none of my fishes really need salt and GH is fine so I have stopped with all that. I saw that once three cardinal tetra died it was because I had got this white stuff on them from the shop. It was not loss of salt
  • Aug2019: I got an upswing of cyanobacteria (these days not categorised as algae at all, but the names slime algae, blue-green algae and smear algae are still in use) [7].
    • I had replaced 1/3 of the water weekly, I had cleaned the sand and the aquarium. (But when i digged further into the sand I saw that there was even more dirt.) I had the skimmer pump and new gravel water quality (below) installed. I had stopped with salt and GH salt. The slimy stuff came back fast, like a day or two after cleaning, and after a week it was not nice. (Even if the fishes did not seem to care.) I started to clean the plants and glass and sand especially, since it came off in flakes. These bacteria live by photosynthesis, so my LED spectrum or lighter days and nights here in Norway, with sunshine some times hitting the aquarium  (when I had forgotten to bring the curtain down) must have been top of the menu for the slime. I had set the light intensity down to 1/3 (but I had also tried increasing it to 3/3 to see if the proper plants then would take over in the balance). I brought the day time in the aquarium down from 14 hours to 12 hours
    • But I gave up and asked for chemicals. I bought Happy-life algin-extra (against «primarily blue-green algae as cyanobacteria and slime algae») at my local aquarium shop [8]. It seemed like the cyanobacteria did not come back. After the four week cure it looks like wonders. The active ingredient the product is salicylic acid 35mg/100ml ([9] – but it’s also printed on the bottle) which breaks some cycle in the bacteria’s energy supply circle. (This also is the active incredient of algin-regular (below)). It’s also a plant hormone, which you can tell me! The plants grew quite a lot. But they became brittle and fragile; and when the cure was over they did not continue growing. So my LED case is not closed. But I am working on it (Sept2019)
    • I took up aquarium salt and GH-salt at half doses (for the catfish – if they even survive the cure. I hope some normal algae will survive.. They all seem to have survived)
    • Two months after having used half dose of algin-extra I had too much black algae. I had also tried a month without anything. I now am trying the Happy-Life algin-regular (against «all algae, but not blue-green algae: use algin-extra in that case). The interesting thing is, as already mentioned for algin-extra, that the active ingredient is salicylic acid 35mg/100ml). Same active ingredient, same concentration, same usage – but different product. Don’t ask me how this is possible!
    • Norwegian: blå/grønn-alge, blå-grønn alge, blågrønnalger, BGA, cyanobakterier, salicylsyre, salisylsyre

Next chapters

This note is by no means finished. But I fill in the chapters here on an irregular basis. (More than I would think!)

The manual

Figure 2. Control box manual, page 1

Download all pages here (41.1 MB). The present is from 27Jun2022.

It might be of some value to download the manual even if you don’t understand a word Norwegian..



The regulator does 25 degC. This is probably OK for all. The living creatures I have in the tank, the regulator’s range (we do have a night temperature lowering of four degrees (only electrical heating, so that’s possible), and how hot it may be in our house.

No cooling

Cooling the tank would have been nice for a few days. We don’t have an air condition, as that isn’t much needed in private homes in Trondheim

At the time of writing this paragraph (late in July 2018) we have had 34 degC outside in Trondheim, and with all windows closed (we don’t have heat pump that could be reversed for air cooling) I have seen max 27.2 degC in the tank (worse, see Max temp read, below). When I was going to do the weekly partial water renewal of 30/3 = 10 litres of water I inserted 26.5 degC into the 27.2 degC and I could see that all the cardinal tetras were swimming like they were playing into the current from the incoming, cooler water. I had not seen that behaviour before, when I normally insert 25.0 degC into 25.0 degC. I infer from this that 27.2 degC is too hot for them, since they seemed to rather enjoy 26.5 degC – even if they didn’t look bad in the 27.2 degC. But is this correct? But I wonder if I correctly can read them like this, because:

Max temp read: 28.8 degC in the tank 31Jul2018! Terrible. But the cardinal tetras seem fine! According to Wikipedia’s Cardinal tetra article (below):

They prefer warmer water temperatures [above 24 °C (75 °F) or warmer]… The preferred temperature range of the fish is 26 to 28 °C (79 to 82 °F). However, if necessary they will live at 24 °C (75 °F)

Maybe I should raise the normal temperature?

Help with high temp

  • When the water temperature goes above 0.5 degC above the normal 25.0 degC then I take the light intensity down to 1/3. This is about 5W. From the max of some 15W I then save 10W from unwanted heating the aquarium from the top
  • I also saw that attaching a wet cotton towel on the front and spraying it with water every now and then, and having a small USM fan in front, did have some cooling effect. By measurement I think this took the temp down by 0,5 degC
  • When the room is hotter than the water then I also set up a shield I have for late evenings (to make it more quiet for the fishes) around the two other sides. This was to slow down on heating the water from the air



You can find all my trials documented here (18 MB). But this is my present try (on the top in the document):

Present lighting scheme

See Lighting scheme to Oct2019 and after Aug2022 and The log (01Aug2022).

Lighting scheme from Oct2019 to Aug2022

See The log (01Aug2022).

Update 24Mar2020: My Echinodorus bleherae [(14]) plant is growing! It is large, so this is the only plant I have. Max light. I guess this is the first plant that has not just withered. I cross my fingers! (Update: it lived for half a year.) I use Happy-Life Algin-regular and Algin-extra anti-algae, half dose, every second week, therefore one month between each type.  That controls the algae very well and also keeps cyanobacteria away. I also use Premium Nutrition in the water (without nitrogen) every day. (Update: I should presumably have fertilised the roots in the gravel, search for «bleherae» here.) Plus a small dose of salt and GH salt every week, when I replace 1/3 of the water. All fish seem to thrive, even the catfish.

  1. I use nine of the ten LEDs from Plant Tech‘s fixture called PlantLED PRO60 (bought just down the street at Mikrogartneriet‘s shop in Trondheim) (Standard Disclaimer). I told that I should use them for water plants, and they thought it might work. But of course they could not guarantee. And after all, using other LED types may not help at all!
  2. The LEDs are all white only. Plant Tech tells me that this is the trend these days; to use wide spectrum LEDs instead of adding coloured LEDs. I do understand that point, since in my experience (below) it’s probably just as hard to hit the right frequency with coloured LEDs, and if not they would be all wasted
  3. I dismantled the PRO60 fixture and cut the single LED strip in three (the extra one LED would be for my haberdashery box) so that I could use each smaller panel with 12V. The list has 10 LEDs in series, nothing more. Great! I added three 3 Ohm resistors (sum 9 Ohm) in series with each 3-LED panel. I have three such panels, as always: front, center and back. The current through the resistors and LEDs is 0.39 A. This is well within the max of the LEDs. Each resistor draws about 0.5 W, and each LED about 1.1 W. As always I used zinc oxide heat paste (thermal compound) to make sure the temperature of the LEDs is as low as possible. I have measured, the temperature in the LED compartment is not above 35 degC. I still added an 84 degC thermal cut-off fuse in the compartment, for the case where the ventilation holes may be obstructed
  4. Light measuring set-up: is a PeakTech 5025 digital lux meter, 30 cm from the panel with no matte glass in between, and the probe laying still in the middle. I got these illuminance values (lux, lx):
    1. Front alone 1220 lux
    2. Center alone 1190 lux
    3. Rear alone 1140 lux
    4. All on 3500 lux (not too bad!)
  5. I don’t know the spectrum of these diodes, except that the white are «Available in no CRI minimum white, 70-, 80- and 90-CRI white, royal blue & photo red» according to the data sheet. Hvar this means for coloured LEDs I don’t know, but for a white I assume it indicates a rather ok light as compared to sunlight
  6. Therefore I don’t know how well the hit the different photosynthesis-wavelengths as discussed below. PAR/PPT
  7. How will these diodes behave for the red chlorophyll a photosynthesis P680, which some say is a good idea? (Search for «P680») in this note

Circuit diagram


Figure 7. LEDs. Download here

Lighting scheme to Oct2019 and after Aug2022

And below is my previous lighting scheme (update: until I took it back again, see The log (01Aug2022)). The reason I took it back is because I was not really successful with the Plant Tech‘s fixture called PlantLED PRO60. I ended up with too much black algae, even with 1/3 light and using «that» anti algae stuff. However, from here and below in this chapter, I have not changed a word:

Previously this ran for a year. I am of course not certain that it is the LEDs that are the problem, since I can’t ask the plants. But with this scheme the plants only died more slowly:

The aquarium has lighting with a total of 15.25W from mixed types of LED strips with 171 LEDs and more than 1210 lm (coloured strips unknown light power (lumen, lm)).
– Since different photosynthesis regions basically are a matter wavelengths (below), I should probably be around blue (450 nm) and red (660 nm) for good «PAR photosynthesis» (Photosynthetically Active Radiation, see Wikipedia below) and gpn mag [1]). Or as often seen, mostly in the 650 nm to 680 nm red range.
– So I must only hope that in this jungle of mostly colour temperature in Kelvin (that’s what they give me (plus CRI, see below)) that some of the wavelengths that are required would appear. More theory in this note later on.

  1. Channel 1: 3.25W total (from three strips) coloured with
    1. 18 LEDs blue (465 nm). This shouldn’t be to bad a wavelength
    2. 15 LEDs green (565 nm). See [5] about green light and photosynthesis
    3. 18 LEDs red (625 nm). This may be too low a wavelength. But according to [4] it doesn’t look too bad. Also, in the PAR Wikipedia article (below) «The YPF curve indicates that orange and red photons between 600 and 630 nm can result in 20 to 30% more photosynthesis»
  2. However depending on the Colour Rendering Index (CRI) and PAR amount of the white LEDs they should contain, more or less, light from the full spectrum, including blue, green and red (of some frequency) (I hope..):
    1. Channel 2: 3.4W (from one double-strip) white of 4200K with 48 LEDs 440 lm
    2. Channel 3: 8.6W from these two:
      1. 3.6W total (from two strips) of white of 6000K total of 48 LEDs 390 lm
      2. 5.0W (from one strip) of warm white 3000K with 24 LED 380 lm
  3. Same light measuring set-up as in the previous chapter:
    1. Channel 1 (center) alone 400 lux
    2. Channel 2 (rear) alone 810 lux
    3. Channel 3 (front) alone 2030 lux
    4. All on 3190 lux (not too bad!)

LEDs 1, 2.1 and 2.2 are «high intensity» 100000 hours from Inspired LED (but 25000 hours to 90%? I don’t know). I have troubled with three other LED combinations, none with explicit red and green, and one with probably too white light. Therefore I added LEDs point 2.4, which are on a strip from North light (Clas Ohlson). The above LEDS with 2.3 instead being a 1.4 W 6000K probably was too white (even with the colours), nothing but algae grew! The present combination is new on 19Oct2018, so I’ll keep you posted. (Figure 1 above shows the aquarium before introduction of the coloured strips and with less white intensity.) I know some say that green is for colouring only, but my web research shows that green is in fact also needed (here). Besides, it needs to be there to make the sum white-ish when blue and red are present. I am now testing plant types more specifically, to see if I have any luck (combined with nutrition and light intensity). Here is some comfort as to why LEDs are difficult, see [2].

Control of my LEDs by SW

  • LEDs are controlled with day/night with gentle morning rise and sun-dawn intensity control that each last for 30 minutes. Light changes at 0, 10, 20 and 30 minutes and the steps are soft
  • There also is a random cloud simulation effect with soft light level shifting.  It basically takes the light down in the average every second hour for 3-10 minutes to a random entry in an intensity list. This may be switched off
  • Also, the length of the day may be set to 14, 12, 10 or even 8 hours. I use 10 hours light on at the moment

As you may see above I have been experimenting quite a lot. At the moment (Sep2019) my plants don’t really live, they slowly die. Even if I add fertilizer. I have not started adding CO2. And I have been wondering whether using pulse-width modulation (PWM) disturbs the biochemistry since light is either fully off or fully on at 222 Hz. But I found a «biased» article that seems to think that at least PWM is ok [10].

As seen above I have three light channels that I control with three SW-driven PWM (pulse-width modulation) outputs. They basically do 1/3, 2/3 and 3/3 individually for each channel, with soft light changes that lasts for about seven seconds for every step. When 3/3 a channel is all on 100% of the time, not even a short pulse left. Code is written directly in xC. PWM frequency is 222 Hz (1500 ms period) and FETs would pull the LEDs that have a common 12V. This flickering is invisible for me, by a large margin (I could see 55 Hz),  and should be ok for most biological life [6]. EMI noise is avoided by limiting the rise and fall times of each power FET transistor’s output pull.

Aside: I see that commercial LED lights typically are controlled by PWM, 0-10V signal or the DALI protocol. See Wikipedia (below). I had no criterion to do anything standard, but it’s nice to see PWM mentioned.

What nanometer to hit which photosynthesis?

Excite Lighting GmbH has quite some interesting notes about LED and photosynthesis. I think the company mainly is in the plant-above-water business, but I am not certain how much this matters. However I did read «light spectrum which applies to all plant species and in all growth cycles» on a product page, so I guess that might include aquarium plants as well.

I have tried to analyse a figure and the accompanying text present in one of the Excite notes, BLUE AND RED LIGHT IN PHOTOSYNTHESIS [3]. I think I found some discrepancies. (The source of the curve is not given, but the PAR Wikipedia article (below) naturally also shows this phenomenon.) I also added a light spectrum from Wikipedia. Press to read as PDF:

Figure 3 – Analysis by me of a figure and text by Excite (press for PDF)

The original wavelength axis is quite confusing since it has a 30 nm/part and the numbers some times won’t match, so it is difficult to read and compare it to the text. Therefore I made each 10 nm also lined. I think that according to the figure and not the text:

  • Chlorophyll a (Wikipedia)
    • violet blue to blue peaks at 420 433 nm
    • orange to far-red peaks at 680 663 nm
      • Plants in water and cyanobacteria, at 680 nm. Search for «P680» in this note
  • Chlorophyll b (Wikipedia)
    • violet blue to green-blue peaks at 480 457 nm
    • yellow to red peaks at 630 650 nm
  • Beta carotene (vitamin A, don’t know if my aquarium plant needs this)
    • Peaks at 458 nm and 480 nm (figures not given in the text)

Disclaimer: this is all based on me hitting right with the positioning of the 700 nm point.

There is a figure also at Wikipedia (here) that is even less accurate than the above.

Where this takes me in the search for simple(r) LEDs for my aquarium is difficult to conclude.

However, just by coincidence I found a four year old paper (2012) [4] that shows that LEDs are indeed possible. Excite also shows this, I guess. But «good» LEDs come at some cost. And is this for my thin light fixture that I guess could allow at max 20W?

I was also pointed to a rather good overview (albeit in the view of torchlights, not aquarium), see [13]. Still, there may be something to pick up there. Thanks, Mark!

Water photolysis

In Wikipedia’s photosynthesis article (below), same chapter title as here (read here) I see that

..requires an external source of electrons to reduce its oxidized chlorophyll a reaction center, called P680. The source of electrons for photosynthesis in green plants and cyanobacteria is water.

I have had problems with cyanobacteria (but it’s under control with half dose salicylic on a bi-weekly basis). But I have still heard that concentrating in the P680 for plants works quite well.

Experimental boards to test LEDs for «horticulture»

This is just for reference. I have not used any of these.

I have recently (Sep2019) discovered that the word «horticulture» is used a lot. It is about plants living in air, not in aquarium per se. But the tools I have seen really only have «buttons» to turn and then one can test for oneself, which is fine. But I read that many of the aquarium plants are grown emersed (rised above water, as opposed to immersed meaning into the water) [11]. So maybe horticulture is ok. When I have searched for LEDs for «plants» I have had little success at f.ex. Digi-Key. But searching for «horticulture LED» makes so much more sense!

Elektor magazine

See [12]. (Thanks Geir Tore for tipping me about this!)

Water quality

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2022.02: still fighting, after all these years

I still have problems with algae. They grow, the LEDs are the same – and the plants don’t enjoy life. Plus, the anti algae stuff that I have used seemed to now add more algae! I am probably wrong on this, since I have too many other problems to distill out such a simple fact. I think it contains salicylic acid (Happy-Life Algin-regular and Algin-extra).

So I tried 1 ml/10l of hydrogen peroxide (H2O2) in the water (here). Not the day after, I do delay things by week or weeks. Washing the only plant types I have now have (Anubias barteri or Anubias barteri var. berteri) in stronger H2O2 in separate tank. They became quite nice, the black algae is at least delayed. Update: After I saw some dark neon tetra deaths I decided not to use H2O2 in the water! See below.

I have decided to go for plants that don’t want gravel. Then I don’t have to add plant nutrition that only seems to feed the algae anyhow. My gravel is quite greasy and black after a week (lower light, yes), so I have decided to remove all the gravel, week by week. Then go for slate (Norwegian: skifer) at the bottom. I have some already, and they don’t get so much algae on them. Not even on a test sample that has been laying on the flat gravel for weeks. But alas, then my plant cage (below) also goes.

Then all of a sudden I found about half of my tiny fishes dead. They looked ok, until two more died, with white spot or neon tetra disease (List of aquarium diseases). My water analysing strip showed all ok, except chlorine. I mailed the water department of Trondheim municipality and they told that they add 0,06 mg/l chlorine in the drinking water – too little for any fish to care. I can’t even taste it. So my analyser strip simply must be defective.

I had not added any salt to the water, so I hurried doing this at 1 ml/l ≈ 1 g/l. Was it the H2Ohydrogen peroxide that had been too harsh on the skin or mucous membrane of the fishes? So they got sick and died? But a little less than half seem to continue to live..

2020.11: plant box not in undergravel filter’s circuit

Shortening or removing the undergravel filter was not very successful since I gradually saw a build-up of particles in the water. Even if I the Eheim submerged skimmer filter unit runs 15 minutes three times per day and three hours after each partial water renewal once a week. I was used to crystal clear water, quite nice, since I stubbornly don’t want any external filter system. Nor any visible submerged filter unit box. It would look ugly in my small aquarium.

But I couldn’t just undefine the problem with undergravel filter. At least, in my case I have problems with the plants. Since I decided that my LEDs were good enough for them (after n trials), I started with ‘easy’ Echinodorus bleherae and nourishment in the sand: that’s their food plate. They don’t drink nourishment from the water. See 2020.8 (below). Nourishment tablets in the sand, with filter water passing through, would also have nourished the algae. That’s why I shorted the undergravel filter.

Until I think I found a combination of nourishment in the sand and functioning undergravel filter. Here’s the (probably not the first in the world) implemented idea:

Fig.1 Adding a plant cage to the bottom of the aquarium (press for more pixels)

What about making a box (I guess cage would imply a net) for the plants, with no bottom (it would steal volume, that’s why) and solid walls, place it on the bottom (that has a low heat from below, plant the plants in the sand, with nourishment – and then just keep the undergravel filter on the rest of the area? That’s what I did.

The box I made from Lexan polycarbonate plastic, 13 x 13 x 4 cm – since all the bottles or plastic compartments I could find were not suitable to cut away the bottom from. But I had to remove two of the Hagen filter grids that kept the sand about a cm above the bottom, for water to freely flow between the glass and the bottom of the sand. See 2020.1 in the picture. I made a passage for water, so that more water could effectively flow below the sand, for the undergravel filter part. I shorted the undergravel filter for the plants, but I didn’t want to short the rest of the undergravel filter system. When I removed the frames there was some dirt there that I sucked up. I will do that for the frames that are left, as well. (I had sucked up and cleaned the sand regularly with a siphon with thick tube at the end, that would let the sand fall down while the dirt was sucked up. I guess that’s why it wasn’t too bad. I guess one should do this every now and then, to avoid the methane bubbles (see 2019.6 below). But then, not too often, so that some nourishment for the plants stay.)

I kept the fishes in the water during the process. They didn’t seem stressed at all, as I guess they would have been if I had chased them with a strainer, for a temporary location in a naked tank of some sort. To make it even less stressing I did this over some days.

I sucked up the sand with a siphon, and some with a strainer. And topped up with 25 deg water a few times. I washed the sand before I placed it back again, into the newly introduced box. With 1 cm more depth. More sand, a safe place for nourishment – for the plants only.

After a few days the water was crystal clear again. Spec #1 fulfilled. Stay tuned. In Feb2022 I removed this cage..

2020.8: shorted undergravel filter

Update Aug2020: I have effectively shorted the undergravel filter. I bored a hole low in the metal cylinder in Fig.5, and put a round shield on top of the suction point from the undergravel. Now my filtering only consist of the sponges inside the metal tube plus the sponge in the submerged water pump that runs 15 minutes three times a day, plus manually 3 hours after I have stirred it up. The reason for this is that I seem to have some success with the plants Echinodorus bleherae (named after Amanda Flora Hilda Bleher. 5 minutes about it in [14]) and Echinodorus ‘Ozelot Green’ (and now also testing Echoinodorus ‘Ozelot’). All those presumably pick up nourishment via their roots, not their leaves. I then don’t have to add nourishment to the water, which seem to also feed algae. Now I have been adviced to add nourishment capsules into the sand. If I then also suck water through the gravel, then that nourisment could easily cause problems with algae. There rings a bell or two for me now, as I have done capsules in the «as gravel filter sand», and I did quit because of algae! (Thanks, Sverre – the guy at TAM Lade.) Stay tuned. Maybe, if the plants get well rooted they could survive without added nourishment (presumably it’s mostly against iron deficiency (so why not just add iron?)) and then I could switch the undergravel filter back on. After all it’s nice with some kind of biological filter since I don’t have any such externally. I haven’t completely given it up yet.

I don’t know why they call this undergravel filter since the basic, biological filter is assumed to be the gravel itself. I would have called it gravel filter or even sand filter? The basic idea is that there should be water below the gravel, the sand resting on filter grids. Then, in some way negative pressure (suck) should be applied to the undergravel water so that dirt will flow through the sand and eventually clog it. (So the sand must be cleaned from time to time).

2019.6: avoiding lactic acid build-up in undergravel filter

Comment 1
I got a mail from a reader that the anaerobic bacteria’s cell digestion of dirt in the sand may lead to build-up of lactic acid and then methane gas in the sand. And that this is the major objective against gravel filter. Of course fishes die from methane. (But I guess there are other byproducts from this process that would become nutrients for the plants.) Build-up of lactic acid would especially happen in the corners, where circulation is lowest, he pointed out. I have talked with this guy locally some time ago and when I stirred in the sand I did have bubbles coming up. But after that, every week when I renew 1/3 of the water, I use a stick that holds the tube, but that is longer than the siphon. This way I can stir the sand and suck up some of the dirt. (Update: when I instead tested a wide tube gravel cleaner I already had I discovered that my long stick method was rather archaic. The cleaner didn’t suck up the sand, it just danced near the bottom, and so much dirt was released.) After this I only see negligible amount of bubbles. Thanks, Sverre!

2019: Sucking from the undergravel filter through a sponge

The idea is to avoid the rather clunky filter system inside or external to the aquarium. This is my second aquarium where I use that system. But the first with this solution:

Figure 4 undergravel filter

174_fig4_aquarium_with_undergravel_filter_and_air_stone_as_pump Figure 4 – Aquarium with undergravel filter and air stone as pump (alternative view or download is here)

In the figure above W is water, w inside a circle is flowing water. Dirt is d inside a square. G is the gravel or sand. Flowing air is a inside a circle. A is the air pump inlet. F is the plastic filter grid elements (article #A-885 by company Hagen, standard Disclaimer). C is a heavy cylinder of stainless steel that i found in my basement. In the (other) anaerobic area f is a filter sponge, so I guess there will be biology going on there as well. (Biology is everywhere in an aquarium!) Now it’s the air stone s that creates bubbles that will rise through the tube and suck water from below, creating the negative pressure. The top tube ends some cm from the water table so that the air and water will also create a small rotation or current of the water; that’s r. Plus, the bubbles of air dissolve some air into the water which probably does not hurt the fishes.

The above solution came up by a coincidence since I saw that I got much cleaner water when I had to replace a defect vertical tube with an air stone. Since I still wanted to use the gravel filter and I had seen particles with my first negative pressure arrangement I combined. My not successful attempt (for almost two years!) was a higher no C (but a small cylinder still) and no s, and f above the air bubbling start point with air bubbling inside it in a tubular center – with a small inlet of water at the bottom of f. I have no figure of this, but forget it anyhow.

The above figure works quite well. It’s even more quiet from the aquarium. And the water is so much cleaner from particles. Another matter is that I still struggle with the plants. But I have coined that to be a problem with the LED light. As if there are anything in an aquarium that isn’t dependent on everything. It’s the balance that I find so hard to get to. But I am in the hope that this this gravel filter system will also help as a balancing part.

By the way, it’s easy to disassemble and clean the components above. The picture below shows the individual parts. The red matter I think is some kind of silicon that I have cut with a scalpel to form gaskets in the top and bottom of the steel cylinder. (I found so much interesting stuff in the scrap return container when the company I worked for moved location). The whole of it is completely hidden behind vertical slate stones. (Aside: I had to make distance nylon screws on the slate so that the fishes would not squeze themselves and become squezed to death. Now I see that they really enjoy that secluded part of the aquarium.)

Figure 5 – Parts of the bubbling filter system (press for fullpixel)

Four boxes seen

Figure 6 – Controller, ambient temp, USB watchdog and relay output plus 12V/24V powers enclosure below (press for more pixels)

  1. Controller box (right, front)
  2. Ambient temperature (right, middle). I2C in and out
  3. USB watchdog and output box. Two 230V AC relay outputs. Also two open drain outputs (right, behind). See My USB watchdog (and relay output) box, chapter Box with open drain outputs from Loft board. The latter will be used for automatic feeding. One of the relay outputs is used for the skimmer pump (above). The button is also seen (press picture for more pixels), in front, only just visible above and behind the controller box
  4. Enclosure (remodelled industrial PC box) containing 12V for LEDs and 24V for heating (left, on the lower shelf)

Five boxes seen

  1. With the introduction of the feeder (see next chapter and a picture there), the small connector box is also seen. However, it’s not in the picture above.

Automatic feeder

I have made an automatic feeder, see My aquarium holiday automatic fish feeder (for granules). It’s hand carved to my amount of small fishes, and that particular food.

The code (download)

The code may be downloaded from My xC code downloads page, part #174.


Wikipedia: Cardinal tetra. Color rendering Index CRI. Cyanobacteria. DALI protocol (Digital Addressable Lighting Interface). Juvenile fish. PAR (Photosynthetically active radiation) – Photosynthetic Photon Flux or PPF redirects to it. Photosynthesis mentions chlorophyll a P680. PWM (Pulse-width modulation).

  1. Possibilities of LED Lighting by Johann Buck (2011), see
  2. Wikipedia: Grow light, LEDs: LEDs (Light Emitting Diodes), see here
  3. BLUE AND RED LIGHT IN PHOTOSYNTHESIS (15 Jul 2016) by excite Lighting GmbH, see
  4. Regulation of the growth and photosynthesis of cherry tomato seedlings by different light irradiations of light emitting diodes (LED) by Liu Xiaoying, Guo Shirong, Chang Taotao, Xu Zhigang and Takafumi Tezuka. See
  5. THE (IMPORTANT) ROLE OF GREEN LIGHT IN PHOTOSYNTHESIS (Dec2016) by excite Lightning GmbH, see
  6. Potential Biological and Ecological Effects of Flickering Artificial Light at PloS One by Inger, Bennie,Davies and Gaston, see
  7. Eradicate Slime Algae in an Aquarium. Keeping the tank clean and changing the water regularly will help. See
  8. Evolution Happy-Life Algin Extra by SMF Aquaristik in Germany: Update: it’s also printed on the label of the bottle that it contains salicylic acid. Happy-Life Algin Regular also exists. I use both
  9. About the active ingredient in Happy-life algin-extra being salicylic acid: Avaforum thread «Happy-life algin regular/extra -et algemiddel som virker!» (see post 15 by Humunuku). See [8] above
  10. Aquarium LED Lights, Controllers, PWM; What is Best by fishservice (2016), see
  11. About emerse production of aquarium plants by Tropica in Denmark, see (emersed means rised above water, as opposed to immersed meaning into the water)
  12. Horticulture Box [180583] by By Luc Lemmens and Mathias Claußen (Elektor labs), with contributions by Würth Elektronik (June 2019, but also in the 2017 November & December magazine), see
  13. Flashlight Beam Tint Explained about Color Temperature, Color Accuracy and Which Color Temperature Works Best? (but not in aquarium’s perspective), Mark Anthony at Flashlight Geek @ by see
  14. Echinodorus bleherae, story by Heiko Bleher on YouTube, see (Think Fish). More at

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