It's summertime, and heat waves abound. All over the United States, the temperatures are into the high 80s and even 90s or above. Our fish tanks are heating up, and we need to keep our cool. Temperature stress is one of the leading killers of aquarium animals.
The ideal range for a freshwater tank with most tropical fish is 77 to 83 degrees. This will make 95 percent of the fish out there very happy. For a saltwater tank, the range is 76 to 82 degrees. For the reef aquarium, slightly cooler at 76 to 78 degrees is best. If allowed a chance to acclimate, all these systems will tolerate higher temperatures. In fact, in summer months many South American, African and Asian fish, as well as most coral reef animals experience even higher temperatures in their natural habitats. What is harmful to these animals is the fluctuation in temperature.
If you normally set your heater for 77 degrees, and during the day the tank temperature rises to 88, then at night falls back to the 70s, this is what will kill fish. The sudden change in less than 24 hours is too stressful. In order to combat high temperatures, we have to keep in mind its not just the maximum range, but the change on the thermometer at all.
The first step is quite easy. It involves moving the low point of the temperature scale upwards. If you normally set your heater at 77 degrees, move it up to 80 degrees. This will make that fluctuation a little less dramatic. Now keep in mind that whenever you increase temeprature, you decrease the amount of oxygen available to the fish. So you want to make sure you have good aeration. In crowded tanks, it's advisable to add at least one additional air source during the warm months.
Your next option involves actually cooling the tank itself. You can do this with a fan. A fan will create air currents that will take away some of the heat from pumps, lights, etc. It will also allow for evaporative cooling of the tank. If you aim flowing air over the surface of the water, the fan will facilitate evaporation of the water, which will lower temperatures. It's quite possible to lower the temperature of a tank 5 to 6 degrees with just a fan. Keep in mind that the increased evaporation will require top off with freshwater, and for those with saltwater aquaria, the salinity will need to be watched.
You can also take a "big picture" look as well by cooling the environment outside your tank. If you have the luxury of an air conditioner, you can cool the room the aquarium is in. This is a great solution if you are going to spend a lot of time in the room with the tank. However, it can be rather expensive to cool a room solely for the benefit of an aquarium.
The last opinion is a chiller. A chiller is much like a refrigerator in that it uses a thermostat, a condenser and a radiator. It takes the water and chills it, then returns it to the aquarium. Or you can use a drop-in chiller that uses a metal probe to chill the water. These are excellent at maintaining temperatures, but are very costly. They are most commonly found at large institutions, and on reef aquarium systems.
For quick emergencies, there are also some options. For the freshwater tank, you can always add a few ice cubes to the tank. This will allow for some immediate cooling, but keep in mind the fact you do not want to cool too much. For a seawater system, you would need to enclose the ice in double plastic bags, so as not to alter salinity as the ice melts.
There you have it -- a few ways to keep your cool this summer. If you have any questions, feel free to post them on the AquariumHobbyist forums.
Copyright 2003 by Jonathan Lowrie. Used with permission. All rights reserved.