Heating a salt water aquarium – how safe is yours?

We marine aquarists are very keen (or certainly should be) to ensure that the environment in which we keep our reefs and/or fish is as good as it can be.

As well as maintaining high quality water etc, part of our concern should be the safety of the support equipment. We need to ensure that the equipment maintaining the environment does just that, and doesn’t endanger it.

So let’s look at [tag-tec]aquarium heating[/tag-tec]. This is very simple nowadays, as there are various power (W) heater/thermostats available, and it is these items that are mostly used. All that is needed is to look up on the internet or in a book the power (W) requirement according to the net seawater content of our aquarium. Obtain a heater/thermostat in accordance with these recommendations and the job is done. However, is it really safe?

Heater/thermostat devices are electrically safe. They are also fairly accurate in maintaining the required temperature (the design temperature). As is usual, some are better than others. The question asked is are these devices safe for our livestock? The answer is for the most part, yes.

What is meant by “for the most part”. Some heater/thermostats run seemingly for ever and never give trouble. Others can fail, sometimes because the thermostat has failed to switch on as the water cools, but more often because the thermostat sticks on.

In the first instance, the water will cool down and the aquarist may not notice. Seawater cools slowly (dependant on surrounding temperatures), so hopefully the aquarist will notice the problem in time but he/she may not.

The second problem, the thermostat stuck on, is the more common and probably the most dangerous. This is because the seawater will be constantly heated, and its temperature will rise to and probably pass the lethal level. The livestock will suffer and likely die. All that loss of life. Also, if we must talk in financial terms, the financial loss is high. Coral fish and reef items are not cheap!

There are ways that we can give protection to our livestock. The first is to ensure that we have properly calculated the heating power (W) requirement of our [tag-tec]aquariums[/tag-tec].

Then we look at how we apply the heat. The first thing that can be done is to split the heating over two heater/thermostats. So, if the heating requirement is for example 300W, we purchase two 150W heater/thermostats and set them both at the design temperature. In this case if one of the heaters fails to come on, the other is there as a safeguard, at least until the aquarist notices the problem. Also, if one of the devices sticks in the ‘on’ position, only half power is being applied (the heat increase will keep the other heater/thermostat switched off), the seawater heats up more slowly, and if it does reach danger level it obviously takes a lot longer to do so, and again hopefully the aquarist will notice the problem in time.

Another way, which in my opinion offers more accurate and safe heating, is to use an electronic heating controller. These are small usually plastic encased electronic devices, where the heater/thermostats are plugged into the device and a probe is placed in the seawater. They aren’t expensive, are easily set up, and, in my experience, are reliable. Care should be taken with a large aquarium to ensure that the controller can handle the total power (W) required for the heating. The heater/thermostats should be set to 3 deg F above the controllers set temperature (which means the heater/thermostats are always in the ‘on’ position). The controllers temperature is of course set at the design temperature. The controller reacts to the information being received from the probe and switches the heating on or off accordingly. The device I use is a pulse controller. This means that the heating is switched on and off continuously, the length of the pulse in accordance with the amount of heat the aquarium needs. If there had been a power failure and the seawater had cooled considerably, the controller would switch on the heating without break, and revert to a pulse when the temperature got closer to its design level. In warm weather when outside temperatures cause the seawater temperature to rise to or passed its design point, heating would not be applied at all.

Excellent as these electronic controllers are, it is still best to split the heating demand between two heater/thermostats. If one heater should fail (and this is probably unlikely as it would have to be the heating element that failed – the thermostat on the heater is ‘on’) then the other would compensate, and of course the controller would apply the heating for longer.

Some aquarists using an electronic heating controller have two heaters connected to the controller, with their thermostats set 3 deg F higher than the design temperature as above. They then fit another heater/thermostat that is rated at the full heating power (W) requirement of the aquarium, but this time set 3 to 5 deg F below the design temperature. In the example above, the requirement is 300W. So there would be two 150W heater/thermostats connected to the controller set above the design temperature, and one 300W heater themostat not connected to the controller, but connected direct to the mains electricity supply, set below the design temperature. This covers all angles. If one of the heater/thermostats connected to the controller fails, there is another. However, if the temperature continues to fall, the independent heater will maintain it to its set temperature, protecting the livestock until matters are remedied. If the electronic controller itself failed (probably unlikely but any device can fail), then of course the two heaters connected to it would be useless. The independent heater would have the heating power to keep temperatures at a reasonable level until the aquarist sorts the problem out.

Some aquarists might argue that they have a chiller (a cooling device), and state that if a heater caused the temperature to rise by sticking ‘on’ it wouldn’t matter as the chiller would detect the temperature rise and commence its cooling action. Well, yes, the chiller would activate. However, even if it managed to keep the temperature fully down (it probably wouldn’t) what a very inefficient practice! Chillers generally use a lot of electricity, and so do heaters. So two of them on at the same time, fighting each others action? No, thank you.

If you have only one heater fitted to your seawater aquarium, I urge you at the very least…. replace it by going out and purchasing two more. One day, you and your livestock may be glad you did.

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