| Temperature |
This is an area that has recently been going through some changes.
Old school was that a temperature of 74ºF -76ºF was optimum based primarily on the fact that oxygen concentration levels are naturally higher in water that is kept at lower temperatures. Over the last couple of years, many hobbyists have started running their tanks considerably warmer. Average is now around 78ºF -82ºF with some even starting to run them at 84ºF or even higher. The logic is that many of the natural reefs have water temperature up in this range and that running a reef tank cooler only unnecessarily stresses the animals. Also, most tanks now have good surface skimming overflows, significant water flow within the tank and through the sump and high powered protein skimmers all of which contribute greatly to providing good oxygen saturation and gas exchange.
I have experience with temperatures between 75ºF and 84ºF in my own tanks either through design or incident.. My small micro reef tank is kept at around 76ºF -77ºF. I think that this may help with the stability of the tank somewhat. For larger tanks, I use and recommend a temperature of around 78-80ºF. This gives you some headroom if you have high-powered lighting or environmental conditions that tend to heat the tank in the summer. I try to keep my tanks from exceeding 82ºF. I have noticed that some of my specimens start to show stress if the water temperature gets over about 84ºF. This stress may be more a result of rapid temperature change though, than the absolute temperature. In other words, a reef tank is probably going to be happier at a consistent 84ºF then when being subjected to a swing of 80ºF to 84ºF every day.
Probably more important than keeping an exact temperature is to maintain a stable temperature. Some swing is OK and 2 degrees is fine for instance. If your tank water temperature is swinging up to 4 or 5 degrees during a day due to heating lights or from some other reason, you should try to reduce this swing if possible to reduce stress on the critters.
If the swing is caused by a temperature drop at night or during periods of the room the tank is in being very cool, then you may need to increase your heater size to compensate. It is often helpful to use two smaller heaters rather than one large one.
| You can size them to get more total heating power i.e. it’s easier to buy two 300W heaters than one 500W. |
| If one fails to operate, your other one will keep the tank from getting cold enough to cause serious damage |
| If one sticks ‘on’, it will not overheat the tank as quickly and you will have a better chance of detecting and correcting the problem before serious damage is done. |
On the other hand, if the temperature rises during the day due to room temperatures increasing or heat from lighting or water pumps, then you can attempt to cool the water somehow. The cheapest way is generally to use muffin fans in the tank hood. One should be positioned that blows outside (the hood) air across the water surface to increase cooling effects of evaporation and another that exhausts hot air from the hood. A cooling fan in the hood should not be placed to blow directly on the lamps itself since that is not what you are really trying to cool. A fan blowing across the sump will also decrease water temperature due to increased evaporation. A more direct and controllable way to reduce water temperature is through the use of a water chiller. These work well, but are expensive and usually cost somewhere between $500 - $1000.
Further Reading:
Natural
Reef Salinities and Temperatures
By Dr. Shimek
Reef
Tank Temperatures — Another View
By R. Harker
