Heat And The Marine Aquarium


We all know that the occupants of a marine aquarium for the most part (there are cold water marine aquariums) come from warm areas of the world. It follows that these creatures have evolved to live within temperature limits and so the seawater within the aquarium has to be warm.

Maintaining the temperature of the aquarium is easy nowadays as there are available reliable and reasonably accurate submersible electric heaters. One heater is sufficient of course but it is better to have two smaller ones in case of failure, if one fails then the heat is not entirely lost.

The generally acceptable temperature range is between 74 and 80 deg F. This is not to say that a variation between these temperaures is acceptable, it isn’t. The heaters or controlling device needs to be set at a temperature within the range. There will be some variation but it will be a degree or two only which is acceptable as the change will be over a reasonable period. A thermometer needs to be in use so that the temperature can be monitored. Most use a stick-on type which adheres to the outside glass of the aquarium and gives an immediate indication, some keen types check the accuracy of these with a glass one which they dip occasionally into the seawater.

There is more to heat than electric heaters and temperature settings and it is applicable to all marine aquarium types. In the winter and other cooler months the heaters will work to maintain the set temperature. In the warmer months as the natural air temperature rises, the aquarium seawater will heat up and the heaters will have an easier life. This warming will increase during the aquarium’s daylight hours as the lights will come on. Some lighting, for example metal halides, have an impact as they heat the seawater and, in combination with the natural air temperature increase, the rise can be substantial. The seawater could heat up way past the design temperature and into the danger zone. What temperature does the danger zone start at? 84 deg F is the often given figure. This doesn’t mean that as soon as the temperature reaches this figure the fish will keel over and the corals shrivel up! They will however be subject to unacceptable stress and it is possible that overlong exposure could be fatal. Higher seawater temperatures mean a higher metabolic rate for the life in the aquarium. It also means a reduction in oxygen levels.

So it’s obvious that unacceptably high temperatures need to be avoided. There are a few ways of doing this and they are not all ‘high-tech’. For those with medium or large aquariums particularly where metal halide lighting is in use, the chiller is useful. These cool by use of an electric pump taking the seawater through the chiller. The temperature is set say 2 deg F above the heater setting. When the heaters turn off and if the seawater continues to heat up the chiller controls it, switching off when the temperature setting is reached. A chiller is only useful to those with an aquarium where overheating is regular and needs regular attention, either all year round or in the warmer months.

Many aquarists only face temperature problems occasionally and there is a way of dealing with this reasonably effectively. Any cover glass in use should be removed. Then all that is needed is a fan, one of those electric room fans with a fan blade diameter of perhaps 12″ plus (remembering that larger fans move more air for larger aquariums). These are easily obtained and often have a switch which permits the fan to move back and forward covering a larger area. Two types of fan are available, pedestal and desk. There obviously needs to be an electric plug conveniently nearby (watch out for persons tripping over the cable). I use a desk fan which is stood on the ground and angled up, it’s easier to store. The fan is switched to its highest speed and the back and forth motion switched off. The fan is aimed at the front corner of the aquarium so that a cooling air stream flows along the front glass panel and the shorter side one. This causes the aquarium to act like a radiator and shed heat. The important thing with a fan is to bring it into play early and not leave it until the seawater temperature is way overheated. Heat reduction with a fan works but is slow compared to a chiller. It should be stated also that there are those who prefer a pedestal type, this is aimed over the seawater surface to cool. There is an increase in evaporation and this has to be monitored, though automatic systems will deal with this anyway as will the aquarist when the seawater is topped up manually. An electric fan should always be kept well away from any position where seawater – or any water – could contact it.

Looking ahead to counteract problems nowadays is much easier as we have weather forecasts which are fairly accurate or the temperatures of the warm months are well known. Being prepared to protect our delightful marine aquariums is really worthwhile, avoiding any potential disaster.