While parts of this country already has weather warm enough to cause problems with our aquariums, most of us are just starting to enter the hot season, where temperature control of the aquarium might become troublesome. Some of the tricks we can use to help lower the temperature of the aquarium include placing a fan to blow across the top of the open aquarium or sump system to increase evaporative cooling, but be ready to add more water to the tank or sump daily. We can turn off any “extra” submersed water pumps to reduce the induction of heat from their electromagnets, though for smaller circulation pumps like the Koralia or Maxi-Jet Pro, the heat “gain” is probably more than offset by the evaporative heat loss these pumps can provide. If you are using high intensity fluorescent or metal halide lighting, you will need to cut back on the photo-period and drop the total level of illumination to help control heat transfer to the aquarium. (This might be enough of an incentive to switch to cooler LED lighting, since lighting can make up the majority of the heat transferred to the aquarium.) If taking these steps does not drop the temperature in the aquarium to a reasonable level (80-84F), you can float a bag of ice or one of the reusable ice packs, ideally in the sump of the aquarium if possible. You will be surprised at how soon the ice pack will lose its ability to cool. If you plan on using this technique frequently during the summer months, it will be best to have several ice packs and rotate them as they warm up in the water. To keep the fish from stressing too much, adding aeration will always help. For a mini-reef tank, the corals may start to bleach out (expel their zooxanthellae) to cool their body. Increasing the flow of water over the corals can help keep them from overheating. If the combination of outdoor heat and equipment demands make it too difficult to regulate the temperature, then it is time to consider using a chiller.
We offer two major brands of chillers, ones by Coralife and others by JBJ Aquarium Products. Over the years, they have made both brands much more user friendly and now include digital readout thermostats, energy efficient compressors, and environment-friendly types of coolant. Available from 1/10 Horse Power to 1 HP, there is a correct size chiller for most aquariums. Both models are in-line chillers, with simple hose barb inlets and outlets that will fit tubing from 1/2″ ID to 3/4″ ID. This allows the chiller to match up well with most of the water pumps systems you would use with the chiller. Perhaps the easiest set up option is to have a small submersible pump located in the sump filter system to pump the water to the chiller, and then have the chiller spill back into the sump. This avoids calculations of head height and allows you to have better control over the actual flow of water through the chiller. The chiller itself should be placed outside of any aquarium cabinet to allow it to vent away the heat removed from the water. The chiller could be placed in-line with the main circulation pump, but usually the flow rate of this pump would be too fast for efficient use of the chiller.
The manufacturers will post recommended flow rates for the different sizes of chillers, and it is best to stay within their suggested range. The size of the chiller needed will be determined by the total water volume of the aquarium system and the number of degrees below ambient temperature (also called “pull down” degrees) required to keep your aquarium in a safe zone. By way of example, if you had a 125 gallon aquarium with a 30 gallon sump, two 250W Metal Halides, a submersible main circulation pump, and a few Koralia style powerheads running at about 86F, and you wanted the temperature to be 78F (8 degree pull down), you would require a 1/4 HP chiller to maintain this lower temperature. If you were to eliminate the Metal Halides and replace them with LED fixtures, you could drop down to a 1/5 HP – 1/6 HP chiller.
General maintenance on a chiller system is rather simple. Periodically remove and clean the air filter on the air intake side and rinse out the hoses with a mild vinegar solution to remove any slime/hard water deposits in the hoses. It should be noted that on the Coralife chillers from 1/10, 1/6 and 1/4 HP, there is a switched plug that is controlled by the thermostat and can be used to turn on a heater or heating element when the temperature drops below the chiller set point.