How to Build Your Own Aquarium Chiller

55-gallon reef tank
stapp/Wikimedia Commons/CC BY 2.0
  • 01 of 03

    Materials and Cost Considerations

    A small coral exhibit at the Steinhart Aquarium of the California Academy of Sciences in San Francisco, California
    WolfmanSF/Wikimedia Commons/CC by SA-4.0

    You can make your own aquarium chiller with these plans from Don Carner. This is a quick and inexpensive method for maintaining steady system temperature, especially during those long hot summer months.


    Assemble these materials:

    • Dorm-sized refrigerator (1 to 1-1/2 cubic feet)
    • 50 to 100 feet of 3/8 inch hard plastic tubing (vinyl isn't as good a choice here)
    • PVC fittings (90-degree elbows or straight connects, threaded or slip)
    • Aquarium-safe silicone sealant
    • 1/2 inch thin-wall PVC pipe (about 1 foot for the "thru-the-box" connections)
    • Hand drill and 1/2 inch drill bit (or 5/16 inch, if you prefer)
    • Screwdrivers to fit the various hardware of the particular fridge you own
    • Rio 2500 or similar pump/powerhead to push the water through the chiller

    Cost Considerations

    These are estimates for how much you will spend on the project:

    • The refrigerator should set you back $89 to $199 depending on the size you choose.
    • The Rio 2500 runs anywhere from $39.95 (mail order) to $69.95 at your local fish store.
    • The fittings, tubing, and pipe shouldn't run more than $10 to $15, depending on how much and what style you choose.
    • Hopefully, you already have a drill and the bit(s).

    A reasonable estimate is $175 once completed, which is still significantly cheaper than a commercial unit. While not as efficient as commercial chillers, this is a viable alternative and will draw your water temp down surprisingly well. Use a pre-set or variable heater to balance the temperature within the sump and it'll become hands-free.

    Emergency Chiller

    If you just need a temporary emergency chiller to help keep your tank temperatures down for a few days, substitute an ice chest (even one of those inexpensive styrofoam ones will do) for the dorm-sized refrigerator and fill it with ice. Drop the tubing coil in it and you are ready to start chilling.

    Continue to 2 of 3 below.
  • 02 of 03

    Chiller Diagram and Instructions

    DIY Chiller
    Don Carner

    The diagram shows these elements:

    • A: Water in from the sump
    • B: Chilled water returns to the sump
    • C: Freezer compartment with temp probe attached to the inside wall of the cooling box
    • D: 3/8-inch coiled plastic tubing
    • E: The refrigerator housing and inner plastic box


    If possible, remove the metal box that isolates the ice cube tray/freezer section, but leave the temp probe alone. This will give a better overall temperature control within the cooling box.

    The more coils, the better the pull-down effect and the more efficient the unit operates. Depending on the brand/model that you are using, you may encounter insulation between the housing and the inner box when drilling your input/output holes. There is no need to seal the door. You might need access if something goes wrong down the road. Besides, it's a great place to keep your additives that require refrigeration after opening.

    1. Drill your access holes in the top or sides, it really doesn't matter.
    2. Cut two pieces of the PVC pipe about 4 inches each.
    3. Insert through the holes drilled and seal very well with the silicone.
    4. You may want to reinforce these pipes with a little Devcon 5-minute epoxy prior to sealing them with the silicone. This keeps them from sliding back and forth and breaking the cured silicone seal should you want to move the fridge down the road.
    5. Glue or thread your fittings onto these two access pipes. You can use nylon threaded nipples to connect the 3/8 inch tubing coils inside the cooling box. Outside, you can glue slip fittings reduced to accommodate the tubing running from the Rio 2500 sump pump to the chiller and back to the sump.

    That's all there is to it. Remember that the more coils inside the box, the better your cooling effect.

    Continue to 3 of 3 below.
  • 03 of 03

    Using the Chiller

    aquarium fish
    Neil Turner/Flickr/CC BY-SA 2.0

    Set the chiller as close to the sump or aquarium cabinet as possible. The further the run of plastic tubing from your sump to the chiller and back, the greater the line loss due to ambient room temperature. You could use pipe insulation wrapped around the tubing run(s), but this is rather unsightly and not necessary unless living in a very hot/humid environment.

    The operation is straightforward. Remember to keep the flow fast enough to prevent freezing of the coils inside the box. If equipped with a thermostat, your fridge/chiller will be easier to control. Some models only allow you to set the main box temperature, not the freezer compartment. That's another reason for removing the aluminum ice cube divider and tray. The probe that is attached to the wall of the freezer area will now monitor the entire cavity.

    Try to use opaque tubing to eliminate algae growth from the sump to the unit and back. You will probably get the black, smudged variety, not the bright green that you see in and around the lighting canopy. Using the milky-white, semi-transparent variety of hard, plastic tubing resulted in this build-up after six months or so.