Keeping axolotl healthy and cool

The real life Mudkip Wooper Pokemon seen above is an axolotl, a salamander-like animal that lives in only one lake near Mexico City. These adorable animals can be bred in captivity, but keeping them is a challenge. [LRVICK] decided he didn’t want to throw down hundreds of dollars for an aquarium cooler so he built his own out of parts usually used for keeping computers nice and cold.

Commercial aquarium coolers that would meet the requirements start around $300 and go up from there. Not wanting to spend that much, [LRVICK] found a 77 Watt Peltier cooler for $5 and figured he could make it work. Off-the-shelf parts for water cooling CPUs were used to construct the aquarium cooler – a water block on the cold side, a huge heat sink and fan for the hot side, and a bunch of tubing goes up to the tank.

Now [LRVICK] has an axolotl housed in a very professional-looking aquarium that is a steady 65 degrees. He’s got a very nice build, and the axolotl looks very happy.


  1. Josh says:

    Very cool build and those creatures look cute. One thing I’d want to do is put both temperature logging and alarming on it. Possibly even a flow sensor on the pump.

    I wonder how the pump will hold up to the water from the tank. Maybe doing a closed-loop system with a heat exchanger would be better for the long term.

    • lrvick says:

      Well the water in the tank is heavily over-filtered so no signs of corrosion/funk yet. Also according to a breeder I spoke to recently Axolotls can survive in 75F for several days. Some can even last a month or so, but it will eventually kill them. If I come home and the water is warming up I need only move them into a bucket in front of my A/C unit until I figure out what went wrong.

      Considering they are on my main computer desk and I see them every day it should be fine, however I have been toying with the idea of adding an Arduino that is going mostly unused right now for some fun lighting and temp/flow monitoring anyway.

  2. Troy says:

    My only concern with this solution is the inclusion of copper tubing on the water block. I’m not familiar with Axolotls but many amphibians and most aquatic invertebrates cannot handle even trace amounts of copper in their water. That water block will leach more than enough copper into the water to kill sensitive critters.

    • lrvick says:

      The copper tubing you see there are just heat-pipes on the CPU cooler, which are a sealed and mounted only to the hot-side of the TEC, never touching water.

      The heat pipes actually do a fantastic job on pulling the heat off, and are barely warm to the touch. Then again I should not be surprised since this heat sink is made cool CPUs at hundreds of degrees…

  3. Nicodemusbc says:

    One thing to note about building a setup like this is that anything that touches the water needs to be 100% aluminum, stainless steel, or titanium (other metals ,especially copper, are deadly to aquatic life). Many of the expensive coolers are much more powerful than this and are made such that no dangerous metals touch the water. Also, those expensive models are made for saltwater aquariums so they have to resist corrosion.

    • lwatcdr says:

      Looking at the pictures it looks to me as if the water block is anodized aluminum. The only copper I see is on the CPU heatsink that cools the hot side of the TEC. I could be wrong but that is what it looks like to me. I am sure the author will fill us in when he has time.

  4. Dax says:

    Would save a lot more in electricity over the years if he just paid the price and didn’t waste his time running a peltier at <10% efficiency.

  5. Bill says:

    This DIY cooler was #7 on my list of ideas to do some day. Glad to see it was a good idea. My 40 Gallon Saltwater runs warm, so I need to cool it eventually.

    • Matt says:

      If you have a saltwater aquarium, the cost difference between a proper cooling device and a DIY solution is probably not worth the cost of losing your livestock should your DIY solution not be up to par.
      Well, maybe that’s not entirely true. If you built a nice refrigerant-based solution that might be fine. I wouldn’t trust a Peltier though.

      I know on my 55g it could easily cost 2-3x as much to replace the life in the tank rather than buy a chiller.

      I lost a bunch of livestock one time (on a previous salt tank) when the tank got to 100F for a few days while I was out of town. That was not a happy situation.

      • Garbz says:

        As a matter of interest why wouldn’t you trust a peltier?

        I mean these are the devices enthusiast entrust to their massively overpriced CPUs and by virtue of their incredible simplicity they are very reliable, though inefficient. I would rank them as more reliable than a refrigerant system over a longer term, and in any case if you’re worried why not include a high-temp alarm in your diy kit?

      • Matt says:


        Peltiers are great on a little freshwater setup.

        However, if you’re running a 200W-400W metal halide lamp over your aquarium (or more if you’re much over 50G), along with maybe 200W of florescent lighting and water-cooled pumps, that’s a lot of heat to expel– You’d need a number of large wattage peltiers just to do the job.
        So, I would argue for the same reason you wouldn’t build a peltier-based air conditioner for your house (hobby projects notwithstanding), you wouldn’t build one for a saltwater tank. It’s kind of like using a tack hammer to do the job of a sledge hammer.
        My lighting example is on the low-mid end of setups for proper reef tanks.

        I think it’s great for these little freshwater tanks though! (and possibly for nano-reefs, too)

  6. Pup says:

    Just sayin, they’re not ‘salamander-like’, they ARE salamanders.

  7. Olivia O says:

    They’re as much salamanders as we are apes. Technically true, but pretty different.

    • Aaron says:

      So exactly the same, then? That we’re an unusual kind of ape doesn’t make us not a kind of ape; that an axolotl is an unusual kind of salamander doesn’t make it not a kind of salamander.

      • steve eh says:

        i have to throw in a quote…really nothing to do with this Amazing build…but here goes
        “It’s kind of amazing that people are still willing to argue that humans didn’t come from chimps, especially now that they’ve mapped out the human genome, and discovered that we’re 96 to 99% chimpanzee. What does it take for people to admit that we came from them? I have a bit about it in my act, “if I gave you a sandwich, and it was 99% shit and 1% ham… would you call that a ham sandwich?” ”
        – Joe Rogan

    • Charles says:

      @steve eh

      No. Humans did most certainly NOT come from Chimps. Chimps and humans have a common ancestor from which both diverged a long time ago. Both have evolved since.

      • Mike bradley says:

        If we came from chimps, there would be no chimps left

      • Adam says:

        Right! We can from the same branch of the evolutionary tree as Chimps but that branch has… well branched off to make us and them. There are very few animals on earth that have not evolved in millions of years, and we are talking animals on the bottom of the ocean (miles deep) where the habitat hasn’t change to have the need for them to change also. Chimpanzee are not one of them, they to have evolved as we have.

  8. JJones says:

    They had one of these in a hostel in Varna, Bulgaria. They referred to it as a Mexican Salamander and it’s worth a google.

    While you are at it look up the Praying Mantis Shrimp…

  9. MattyMatt says:

    The materials and coatings are a definite concern, though the pump and other materials appear to be aluminium as stated previously.

    There are a few ways you can check this, a quick search yielded this site:

    (there is a copper test there, as well as other heavy metals you can test for)

    I’m sure there are many others out there, with probably very similar tests.

    I’ve had all kinds of aquatic creatures over the years… though never axolotls. I am fairly familiar with the chemicals and affects of other chemicals involved with keeping aquatic life happy.

    I would defiantly have some sort of management/monitoring solution so your cool little creatures don’t succumb to heat!

    Either way, great build and keep it up!

    • lrvick says:

      The only copper touching water is thin piece inside the water block at near freezing temps so I expect minimal solubility.

      Just for peace of mind I will be keeping a close eye on the water with this:

      Axolotls also start spotting and having dulled colors as early warning to any copper poising, and their complexion is still very clear and healthy.

      Worst case I mill out an aluminum replacement for that small part at my local hackerspace.

  10. Kyle Hotchkiss says:

    Aw! That is an adorable creature! So given how sensitive they are to the environment, how’d ya bring it home?

  11. kabadisha says:

    I used to work for a pet shop where we sold these little guys. We just used to keep them in a tank at room temperature (around 20C) and they did just fine.
    All we did was keep it out of direct sunlight and away from heat sources. We even had goldfish in there with them.

    Nice implementation though! – Would be good for anyone looking to keep a cold water setup on a budget.

  12. muriani says:

    So… when should we expect to see a fully-formed ghola from this axolotl tank?

  13. lrvick says:

    Hmm, that could be fun.

    Perhaps I should toss in some radiating materials, or random bits from the back of my fridge…

  14. Nedim says:

    so i live in Bosnia and i found animals just like thes (jus a little smaller) in a small lake
    so my question is :D
    are they the same animal or?
    (sry for my bad english :P)

  15. Abbott says:

    I agree with everyone else, peltier’s are horribly inefficient. Though, I was looking through Ben Krasnow’s blog, and came across what seems to be a possibly better/more stable solution. He uses a drinking water chiller that he picked up for $100 from wallyworld or someplace.

    Original post:

    Update stating success:

    Update with a Ti heat exchanger:

    • lrvick says:

      Most of these drinking water coolers are TEC based. The Avanti brand pictured in Ben’s post frequently advertises “Compressor-free Thermo-Electric Technology” which means it is probably another fancier TEC based implementation anyway.

      At a glance this seems like just a very bulky abstraction opposed to using a TEC directly, with probably as much or more power consumption.

      I actually read this very article before setting out on my project here. Ben had indicated problems with turning TECs on and off constantly, and bleed-back.

      First off, bleedback could probably of been avoided by simply always stopping the pump and the TEC at the same time so your not pumping warm water back into the tank. Secondly, yes its probably not good to turn the TEC on and off constantly. If there is need to toggle power on it so much, then it is probably better to just use a lower wattage TEC altogether so it can just be left on. TEC inefficiency grows with each wattage step anyway.

      I only use a 77w TEC which is just enough to maintain a 10-15 degree drop below ambient for my 6 gal. Granted, it takes several hours to bring the temp down at wattage that low, but that’s just fine in my situation.

  16. Hirudinea says:

    These axolotls are really cool, and if you shoot them up with iodine they’ll turn into salamanders (and die, its a hard transition).

  17. adam says:

    do you like mudkips?

  18. JB says:

    You can always keep them safe in their Pokeballs :P

  19. Nedim says:

    here is the pic ^^

    i found just this one
    i culdnt catch a bigger one :/

  20. Hal Jones says:

    Wow that axolotl’s pretty cool, never heard of one before. Might look at getting one for my tank!

  21. Graham says:

    Is there any way this would work with the cooler pressed against the side of the aquarium, rather then making a block / pump system?

  22. Dylan King says:

    Check this out for a cheap aquarium cooler hack :)

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