My aquarium notes

Started 24Jul2018 – updated 31Jul2018

This page is in group Hobby and will become a blog note about my little aquarium. It has been a year since I introduced fishes to it, so it’s about time.


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. There is an overtemperature 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
  • 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
  • Cooling the tank would have been nice for a few days. But the temp seems to have maxed on some 27.2 degC so far. We don’t have an air condition, as that isn’t much needed in private homes in Trondheim
  • I am hoping to be able to squeze in a radio board and SW to the controller box to export some of the values. And then pick up the values in a logger unit with a web server
  • The aquarium has lightning with a total of 11W from mixed types of LED strips: one 2W 465 nm 24 LEDs blue, two 2W 3200K 24 LEDs, two 1.4W 6000K 18 LEDs 150 lm and one 2.2W 6000K 30 LEDs 240 lm
  • LEDs are controlled with day/night and random cloud simulation with soft light level shifting
  • 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 three DC power sources: 12V for LEDs, 24V for heat and 5V mobile charger with micro USB for the controller box
  • There is an under gravel filter, vacuumed from a tube of raising air
  • The air pump is in the basement below. No motor or pump noise
  • For the fishes I only have some ten cardinal tetra plus two armored catfish and a nice little shrimp. They seem to be quite happy. I hadn’t forgotten, I said so
  • Plus, too much snails
  • 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
  • A 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..

Next chapters

I should have time for this in the autumn of 2018. I will, however fill some odd chapters here, more like a scratchpad, before I encounter on the more structured note:


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

At the time of writing (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?


Wikipedia: Cardinal tetra,

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