Most people are familiar with standard aquarium heaters because cold water is the most common aquarium problem. However, some fish breed in these lower temperatures and require special equipment to maintain a comfortable temperature.
To cool the water, most people install an aquarium cooler. Aquarium coolers are expensive and very easy to make yourself. You can also buy JBJ Arctica Titanium Chiller 1/10HP (DBA-075) via Marine Depot.
All you need is the smallest refrigerator your department store has, a 100 ft. 3/8 inch plastic pipe, a 90 degree PVC threaded bend, a 3/8 inch hand drill, a screwdriver, retractable pipe cutter, non-toxic silicone sealant, and a pump that strong to force water through the system.
You will want to shell out a little extra cash on a quality pump or all your hard work will be for nothing. First, drill two holes through the top of the refrigerator. One goes through the freezer and the other is right next to it, right through the fridge.
The water in the tank enters through the non-freezing area, flows through the pipe, and exits the freezing area in the tank. Insert your PVC connector into the hole you just drilled and seal it nicely with epoxy silicone. Add several layers to ensure that no cold air escapes from this access point.
Cut any pipes to connect the tank to the pump, the pump to the refrigerator, and the freezer to the tank. Fix this pipe properly and make sure it is waterproof. Roll up the pipe in the refrigerator and glue it to the fitting. Make sure everything is tightly closed before moving on to the next step.
The only task that remains is to turn on the pump and refrigerator and maintain them. If you need an urgent solution and don't want to buy a refrigerator, you can always follow the same procedure replacing the chest with ice.
Run the coil evenly over the ice and turn on the pump. This will only continue as long as the ice remains cold while other models can wait for the aquarium indefinitely. Also, consider adding a thermostat heater to ensure the water never falls below your fish's comfort zone.