Featured PostsHackerspaceMain Stories

Thermo-Electric Axolotl Cooling

So in my many ventures around the interwebs I eventually ran into a picture of an unusual animal, the Axolotl. Over the years I have cared for and been aware of a lot of exotic pets but this… this was something totally new to me.

On seeing pictures of these for the first time I did some research, then did some more research. Turns out they are a listed as a critically endangered species existing wild in only one lake in the world. Specifically, Lake Xochimilco in a valley in the mountains of Mexico. I also learned they have some very fascinating properties such as their ability to regrow just about any body part, and some glow in the dark. If threatened, some will even permanently sacrifice their regenerative abilities in order to drop their gills, grow full tails, fire up a set of lungs, and begin life on land as a salamander. These things are like legit real-life pokemon that can “evolve” and everything.

So learning all this I decide I want to procure a couple of them as pets. I found they can be bought online from Phil Vena from buy-axolotls.com who has been breeding them in his basement for several years. He has started a rescue program, as well as efforts  to educate people about these fascinating animals as well as helping introduce new colors and traits to the species. I spoke to him at length a few days ago and was very impressed by his knowledge and care for the animals, and would highly recommend him to anyone who decides they want axolotls of their own.

Anyway, so I got a couple ordered, then shortly after read a warning I somehow did not register before. Despite all their regenerative abilities, 75F or higher will kill them. Considering I live in Orlando, Florida… thats a problem.

Right away I thought back to my years of cooling overclocked computer CPUs with liquid circuts and Thermo Electirc Cooling Elements (TEC). In short when electricity is applied to a TEC one side gets very hot, and the other gets very cold. The hot side must be controlled however it will quickly build up too much heat and cook itself.

I however wanted to not jump to a hard solution if there was something cheap and available to do this for me. The best thing I could find on the market to help cool a small tank like my Fluval Edge was the IceProbe, at about $120 shipped. Considering the fact that its maximum temperature drop is only 3-6 degrees at best, and that it would not even fit in the tank… I looked for external cooling options. Cheapest external cooler I could find was an Aqua Euro USA chiller at $290. Thats the lowest end of these units, most at well over $500. There is also the fact it would be a huge brick nearly the size of my tank I have to put somewhere. These facts didn’t sit well, so I then jumped into #familab on IRC to discuss the TEC based DIY options.

After looking at some TEC prices, and finding they are only about $5 for a 40mm^2 77watt unit, I thought building it was probably a smaller and less expensive path. On talking to Kyle on #familab to IRC he helped me pick out some compatible parts to sandwich the TEC and give me the final push I needed to just make it.

Ordered it all that night and a couple days later brought it all to Familab for the 2011 Holiday Party.

Had to mill out some holes that did not quite fit and then Kyle and I got it all put together. Hot side of the TEC gets a conventional universal mount Fan CPU cooler, and the cold side gets a universal mount water block CPU cooler. The 40mm TEC unit was a perfect fit between them.


We then set up a water pump to pull water out of a 2 liter bottle, through the water block mounted to the cold side of the active TEC unit, back out to the bottle. Within a few hours the bottle was down to a brisk 53 degrees. Success!

Next I took it all home and got it all integrated into my tank, and let it run. Several hours later it was down to 65F, and considering Axolotls are happy anywhere between 40-72F, this would do perfectly.

I then added a digital thermometer I got off Ebay for a couple dollars by dremeling out a hole in the front bezel and used some coat hanger parts to build a bracket to hang it. I also added a power rod to wire it all up neatly, and then introduced my two new pets which were previously living in buckets in front of my air conditiner.

I now have my Axolotls happily living on my desk next to me. When I get frustrated with a programming challenge I can just look over and go “You are very strange creatures, and you amuse me” then go back to my work refreshed. Though I may well make some modifications to this design in the future or invest in a larger tank at some point, I am pretty happy with how this setup turned out. It seems to be a perfectly viable option for people who need to keep cold-water species that don’t feel like shelling out about $300 on a commercially sold  water chiller.

Here are some pics of the “finished” product:









And without further ado, lots more pictures:

16 thoughts on “Thermo-Electric Axolotl Cooling

  • Pingback: Keeping axolotl healthy and cool - Hack a Day

  • fernando

    Have you considered that a failure on the peltier could cause a lot of trouble? Adding a backup system would be wise, with an integrated circuit to keep monitoring the main system. In case of failure, the secondary one takes place.


  • If that CPU block is copper (most are) it might be deadly to your pets. Check out what the block is made of (and/or plated with) to be sure it won’t harm them. Also, an in-line filter might be a good idea to help that pump as most computer WC pumps aren’t meant to run with debris in the water. Other than that awesome job!!!

  • Will:

    The water is heavily over-filtered so it should not cause any problems for a while if it does, however I have been thinking about an in-line filter, though I have yet to find any small compact ones. If you know of any you recommend please let me know.

    There is only a small copper plate in the water block at near freezing temps so I expect minimal solubility. These animals also show early warning of copper poisoning via spotting/dulled colors, and they still look very healthy.

    For peace of mind I will be keeping an eye on the water with an API copper testing kit along with my regular aquarium water testing.

    Worst case I can always mill out a replacement plate out of aluminum at familab.

    These can survive for several days, and some even a month or two at 75F. For short periods of time it just stresses them out a bit and spikes their metabolism. I see them every day on my desk so if the system fails for any reason I will catch it fast, and can just move them to a bucket in front of my A/C and then figure out what went wrong.

    I am toying with the idea of adding an Arduino for some fun monitoring and stats though…

  • Pingback: We need no stinkin... aquarium chiller? - Home Brew Forums

  • Pingback: Keeping axolotl healthy and cool | CisforComputers

  • Raiden

    Nice work, but Axos would need a bigger tank than that at adult size, possibly 40G for a pair.

  • If your system is working properly and you decide to throw in an Arduino, make sure it only does readings and no controlling at first.
    As long as it can’t interfere with the working system it’s fine, because the Arduino core lib is notoriously unreliable and should not be used in critical applications.

    If you decide to also have it control the system, make the code watchdog-timer based!

    I’d hate to see your pets die because of some coding mistake 😉

  • Pingback: Enfriador de Acuario Hecho en Casa | Robotikka

  • Matt

    Did you build the tank yourself? The setup is flawless. I breed corals in saltwater aquariums and I had not considered rigging my own cooler before that is something I gotta try.

  • Pingback: Ways to keep tank cool!!! - Caudata.org Newt and Salamander Forum

  • Pingback: Bogwood???? - Caudata.org Newt and Salamander Forum

  • luigiarmato@yahoo.com

    Was thinking you got an awesome set up there. I got a fluval edge and was wondering how big is yor axolotls in inches. Cause am thinking of getting one my self but reading loads of sites saying our tanks to small.

  • luigiarmato: A lot of the things I see said against small tanks are regurgitated by people who have never owned but a few axolotls themselves or observed behavior. I have yet to see a breeder or researcher that specializes in these animals make such claims.

    I have seen examples of large axolotl colonies like Indiana State just using small plastic containers of perhaps 4-5 gallons.

    I have also personally talked at length to a large breeder who has raised thousands of axolotls and says the small tank arguments are just FUD. He said that in over 10 years of breeding he has seen no negative health impacts or stress signs and that they happily live and breed in 10 gallon tanks with 3 to a tank provided regular feeding and clean water.

    When Axololts are stressed it is thankfully very easy to tell as they curl the tips of their tails. I have seen mine do this when their water was too cloudy or during a fight they had once.

    My axolotls are just over a year old now and about 7 inches currently, eating regularly, very active, and still growing.

    One thing to keep in mind, is the more water you have, the less often you have to clean. Having a small tank that is not kept clean could kill the animals due to toxin build-up. In my case adding ghost shrimp resolved this need as they eat all the poop/algae and keep the water spotless in addition to giving the axolotls plenty of food/exercise. I only have to change the water every couple of months.

  • graham heath

    And is the Axolotl? Any update on the build, or are things humming along?

  • Brian

    Just wanted to say that i stumbled across this post a year or so after embarking on a mission to build my own thermoelectric axolotl chiller. I’ve got my little buddy in a 35gal aquarium that’s about 3/4 full and no matter what without a cooler the water is always too warm. I know lower water levels are common but she and I like the level of water as is. I started out with a single tec and heatsink which did little but increase my interest in the potential for TECs. Modded myself a 600w ATX power supply to have two heavy leads of 12v and 5v with amps to spare and moved up to water cooling, and two TECs between 3 small water blocks. Small but functional, but not for the water volume I have.. LOL.. Now I have three 120x40mm water blocks with six TECs sandwiched between them, all cooling the centre block with the hot sides all facing the outer blocks which route the water through a pump and 2L reservoir. Voltage and amperage displays on all the peltiers and temp gauges on the reservoir and cold outflow. All controlled by a relay with temperature sensor in the tank, set to shut off at 17°C. It took a few failures before getting to this stage but this is a very cool efficient and virtually silent cooler. I would use it on anything up to 40g. :). Its also a power pig and if you try building one make very sure you use wire of the correct gauge for everything. Don’t want a big messy fire do ya?

Comments are closed.