Heating the seawater is straightforward nowadays, as a unit called a heater/stat is commonly available. These take the form of a longish tube with a thermostat at the top end and a heater unit at the lower end. They are available from local retailers and online and the price is very reasonable.

Aquarium heaters used to be the source of a few problems in the past with sticking contacts in the thermostats or general failure. Nowadays they are more reliable though the danger of a sticking thermostat is still present. There are ways of reducing the risk but obtaining the heater unit is the first consideration.

The heater/stat is available in several wattages (W) and the size of the aquarium, or rather the net total gallonage of the aquarium which includes any sump, dictates the heating need. The usual guideline is to allow 2 watts per gallon of seawater for a normally heated room. If the room is unheated then the wattage is doubled. So keeping things simple, a 50 gallon system in a heated room would require 100W, and in an unheated room 200W. These wattages are not based on a formula that must be rigidly followed, what is required is that the heating is known to be fully capable for all possible demands. Wattages that are a little higher – within reason – should not be harmful.

It may be thought that buying a bigger heater, say 400w in a heated room, would be better as that capacity will not face any problems ever. However, it is not a good idea. If the thermostat contact sticks in the ‘on’ position then the seawater will heat up more quickly, possibly meaning that the aquarist doesn’t notice the excessive temperature problem until it is too late.

Once the heating requirement is known there isn’t anything to stop the aquarist purchasing a heater/stat of the correct wattage (if the wattage doesn’t match the net gallonage the next heater up should be chosen). Again remembering that though modern heaters are much more reliable than they used to be potential problems have not been totally eliminated, so it is best to obtain two heater/stats. They should not individually equal the full heating requirement of the system, but half of it. In other words, if 200W is required then obtain two heater/stats at 100W each. This will help to prevent a problem with one of the thermostat contacts sticking ‘on’ or ‘off’: if one sticks in the ‘on’ position then the other will turn off when the design temperature has been reached slowing down the temperature climb, or if it sticks in the ‘off’ position then the other heater will prevent the seawater cooling too quickly. Hopefully the aquarist will notice the problem in the extra time the system affords.

With two heater/stats the temperature setting on each should be the same. Many heater/stats are set at 75 deg F before they leave the factory so if the aquarist requires a higher temperature then the devices will require adjustment. This brings up another point: when purchase is being considered ensure any temperature adjustment is easily accomplished. There are heater/stats nowadays that display the temperature setting on a clear scale and an easy to use adjustment knob is at the top of the unit.

There isn’t an absolute requirement that two heating units are used, but for the reasonable extra financial outlay it is worthwhile.

Finally, before parting with hard cash find out what the temperature variance of the heater/stat is. The temperature variance is the difference between when the heater turns off and when it turns on again – in other words the sensitivity of the thermostat. A variance of 1.5 deg F is good but manufacturer’s products vary.

Really that is all there is to consider when obtaining heater/stats, but I’ll just mention one other thing. I should point out that though this is generally desirable for accuracy and dependability there isn’t an absolute requirement.

Some aquarists when setting up a system decide to employ an exterior electronic controller. They can of course be retro-fitted. The controller usually takes the form of a small box perhaps 4″ square or so. There is a mains electricity connection, and a socket from which the electricity for the heaters is supplied. In addition, there is a small temperature probe that goes in the seawater. Temperature is set usually by means of a small knob, and the heaters are shown to be active or not by an indicator light. If two heater/stats are in use, they should both be connected to the controller (ensure the power handling capacity – wattage – that the controller can handle is not exceeded). Once the design temperature for the seawater has been set on the controller, the temperature setting on the heater/stats should be 2 deg F higher. This means that the heater stats are always in the ‘on’ position. Some electronic controllers pulse electricity through the heaters, reacting to the probe readings. If the seawater is trying to cool, the pulses are longer (so the heaters apply heat for longer), if it starting to warm up too much the pulses shorten. It is reported that as the heater coils are always warm, not going from cold to hot and back again the heating coils last longer. These electronic units could control temperature to +/- .5 deg F. It sounds as though they could be an expensive item, but they aren’t.

One way of protecting livestock is by correct husbandry, keeping the seawater quality high, correct feeding and the like. The initial way to achieve this protection is to invest in adequate hardware in the design stage obtaining properly sized powerheads, protein skimmer etc. An important part of this hardware is the heater.

Aquarium heaters nowadays are generally reliable and can be accurate to about + or – 1.5 deg F or better. The unit comprises a heater that is at the lower end of the unit and a thermostat that is at the upper end. The more powerful the heater, that is the higher the wattage, the longer the unit will be.

The heater is best fitted in a sump if there is one as it could look out of place in the display aquarium though in a reef they are usually fairly easy to disguise. If they are disguised then there should not be any interference with seawater flow around them. They should be clear of the sand and preferably fitted at an angle, not vertically, though with modern seawater currents this is not quite so important.

The size of the heater should be calculated according to the total net gallonage of the system. This can simply be achieved by checking the recommendations of the manufacturer. It is usual to also size to the room the aquarium is in – if a cold room more heat is needed than in a warm one.

The heater as said is generally reliable nowadays but, like any piece of equipment, they can fail. They could fail in either the ‘off’ or ‘on’ position. This is a major failure: if a protein skimmer fails then there isn’t a nearly immediate threat to the livestock, though of course it needs attention as soon as possible. A heater failure needs immediate attention not just when convenient.

Dependant on the air temperature, cooling seawater does become such a threat if the aquarist doesn’t notice the problem. Seawater generally cools fairly slowly, the speed based on volume and air temperature. Seawater that is gaining in temperature quite quickly is a more serious threat. This is because if the heater has stuck in the ‘on’ position heat is constantly supplied and the seawater temperature rises continuously, more quickly than it would cool. As the temperature increases so the oxygen content decreases. Further, there is a general upper tolerance level for corals and fish, above which losses will occur.

The potential problem can be guarded against quite easily. When the total wattage required to heat the seawater has been calculated, divide it by two and buy two heaters. So if 200 watts is needed obtain two heaters at 100 watts each. The heaters are set to the same temperature and fitted parallel to each other. Some aquarists put one at each end of the display tank, but if a sump is available they can go in there.

“200 watts is needed so if one fails the aquarium won’t be heated properly.” That’s correct, but the immediate danger is removed. If one heater fails in the ‘off’ position, then the other heater will apply heat and attempt to reach the design temperature. If it can’t reach this temperature it will not switch off. This means that the seawater will not cool down as rapidly and the heater will at least be able to maintain a lower temperature. This means the aquarist has considerably more time to notice the problem before there is real trouble. When a replacement heater is fitted all is well.

If one of the heaters sticks in the ‘on’ position then there will not be a danger of overheating the seawater with the problems that will bring. The heater that is permanently on will obviously continuously heat the seawater. The other heater which is operating normally will reach the design temperature and switch off. The seawater is now likely to cool down though more slowly than usual. When the temperature drops sufficiently the second heater will switch back on again and so forth.

Using two heaters doesn’t cost more in electricity: the wattage is the same as if there were only one. However, the livestock are protected from excess stress or even disaster.

Whatever the warm water system, be it a fish only aquarium or a reef aquarium, the aquarium temperature needs to be kept stable, with only a small deviation from the design point. The majority of aquarists will employ heaters, and the rest chillers, or maybe both.

Modern heater units and chillers are reasonably accurate in maintaining temperature, usually with a deviation of between 0.5 to 1.5 deg F. Seawater is fairly slow to cool and warm, so these changes are acceptable. Wider changes in temperature can cause stress to livestock, the worst affected probably being corals.

On the wild reef seawater temperature is for the most part stable throughout the year. Average temperatures on these reefs are 82 deg F *. Note that this is an average, meaning that some are cooler and some warmer. It gives an idea of where the temperature in an aquarium could be set. Setting the temperature in the aquarium to 82 deg F will give a general average temperature approximation. So is that the temperature to use? As said the temperature is an average – there are variances between reefs and there will be differences at various depths.

The lowest temperature that should be used is more easy to state. Coral reefs (of the warm water kind) do not develop if the seawater temperature is 65 deg F or less. So the temperature must be higher than 65 deg F. However, this is too low for organisms to have a high enough metabolism and it is most likely they came from much warmer water, so they would decline rapidly and die. The lower water temperature acceptable is 75 deg F.

Some aquarists set a temperature at between 80 and 84 deg F. This is done because the metabolism of the whole aquarium is raised – fish, corals, shrimps and the tiny life forms in and on deep sand beds (DSB) etc. This increase in metabolism should mean faster growth. Fish will demand more food, this food will be digested and waste will be processed more quickly. So all should remain more or less in balance. Well, yes, it should. However, the aquarist is moving closer to the edge. The aquarium has a small gallonage no matter how large it is when compared to the sea. The water can heat more quickly. If the temperature is already maintained above 80 deg F, then it is a quicker journey to higher temperatures and potential trouble. What if a heater malfunctions in the ‘on’ position? What if metal halides are in use (the heaters will turn off but the water could continue to heat)? Additionally, seawater that is cold has more oxygen than warm seawater. As the temperature continues to rise oxygen continues to reduce. This could cause trouble in any system, but particularly in a heavily stocked fish only one.

In a well managed aquarium the oxygen question should not arise. A protein skimmer is no doubt in use. Also, adequate water circulation will provide efficient gas exchange maintaining oxygen levels. The point is, the potential for a problem is there.

Apart from potential problems with the example oxygen, maintaining higher temperatures is going to cost more in electricity, except for the aquarist who has to keep temperatures down with a chiller. This is, or should be, a secondary consideration of course, it is the welfare of the livestock that is being considered (and the aquarist: if livestock are healthy and vibrant then the aquarist will be happy).

So, what is the best temperature setting? Lower down, the livestock will have a slower metabolism and oxygen will be more plentiful. Higher, the opposite. It seems a compromise is in order. I would suggest a temperature setting of between 77 and 80 deg F. This is somewhere in the middle of the acceptable range and gives a reasonable safety margin should a heater malfunction etc.

I run a soft coral reef at a temperature of 77 deg F. The corals grow at a reasonable rate – they need cutting fairly regularly. The fish display good appetites, and the DSB has a high population of miniature life forms. I should mention that I have never experimented with higher temperatures – but then, why would I when all is well.

Whatever the temperature, it needs to be stable. Constantly changing the temperature setting will do no good at all. If the aquarist wishes to experiment with higher settings, then the temperature should be increased slowly over a considerable period. The same applies to temperature reduction of any amount. The aquarist who sets a high temperature needs to ensure the heater/stats in use are of high quality, and preferably there is an external heater control with an in-tank probe in use.

(* Reference: Aquarium Corals. Eric H. Borneman)

The aquarium temperature is one of these factors.

Allowing the temperature in the aquarium to fluctuate cause stress on the corals, fish etc which can bring out diseases etc or at worst even death.
[Read more]

Keep the water warm.

Not just warm but at a constant level with as few fluctuations as possible. Fish do not like fluctuations in temperature and corals are even more sensitive to it.

Aquarium heaters come in all sorts of shape and sizes and this is where confusion can sometimes set in.

With aquariums also coming in so many different shapes and sizes you are going to need to calculate the size of aquarium heater needed.

So how do you do it?

Heaters are rated by wattage which determines the actual heat output of the unit.

To calculate the size of [tag-ice]aquarium heater[/tag-ice] needed you calculate how many gallons of water are in the aquarium, do not worry about displacement and then multiply this by five. Therefore if you have a 50 gallon aquarium the heating requirement is 250 watts.

This calculation is a very general calculation and is based upon the theory of 5 watts of heating for ever gallon of water in the aquarium. If you live in a very warm climate then you could possibly reduce the wattage requirements, if you live in a very cold climate then you could possibly increase the wattage requirements.

There are some other aspects which is recommended for you to take into consideration when you calculate the size of aquarium heater needed for your setup as these may mean that you could do with either reducing the wattage requirements or even increasing them.

• What other equipment do you have in your aquarium – other equipment may generate heat for example lights, powerheads, pumps etc
• The ambient room temperature of the room where the aquarium is located both in the day and in the night.
• Where will the heater actually be placed – will it be in the main display aquarium or in a sump.
• Other heating or cooling equipment in your home which are close to where the aquarium is located.

There are some aquarists who calculate the heater requirements by looking at the constant room temperature of where the aquarium is located and then work out how many watts they need to increase the temperature of the water to the desired level. For example if the room temperature is a constant 67 degrees and you want to maintain a heat level of 77 degrees then you will need to increase and maintain the water by 10 degrees.

Personally I find this very hard to work out and to be fair not that accurate – how many homes have a constant temperature?

Probably not many and for that reason I always work the heating requirements out based upon the actual water volume and not based upon ambient temperature. The way I look at it is that if the heater is not required then the thermostat on the heater will turn the element off.

One thing that should be noted is that I normally recommend installing 2 heaters into the aquarium. The reason for this is that if one heater were to fail then the second one will keep the water warm until the other can be fixed or replaced.

In the recommended scenario above then if you needed say 300 watts of heating then I would recommend that you install two 150 watt heaters.

You, of course do not need to install 2 heaters if you do not wish to do so but if the heater fails for whatever reason then you will not have a backup and the water could quickly cool down.

Temperature on the majority of wild reefs remains fairly constant all year. Tests of temperature on some wild reefs have shown variance. The following shows this:

• Average temperature of all tested reefs: 82 Deg F
• Average of reefs with lowest temperatures: 77 Deg F
• Average of reefs with highest temperatures: 86 Deg F

So it would seem that if the temperature of the aquarium coral reef is kept between 77 and 86 Deg F then all should be well. This could be nearly correct. The corals (and fish etc) on the individual reefs have more than likely a tolerance for the temperature on those reefs and also any variation of temperature. This variation has been shown to be as much as between 15 Deg F and 21 Deg F *. These variations do not apply to the majority of reefs but do indicate that some reef’s temperature stability is not as constant as others.

A further and important point about temperature change on a wild reef is that it is slow. The reefs are washed by millions upon millions of gallons of seawater, and the seawater moving over the reefs is of course linked to the seas and oceans, with the colossal amount of seawater this represents. So increases and decreases in temperature are not going to happen quickly. As the system they live in is so stable and changes of temperature are so slow, the inhabitants of the reef are going to exhibit a tolerance to the changes.

Now look at our aquariums. A bit of difference to say the least! Even the aquarist who has a huge aquarium has less than a small thimbleful when compared to the wild reef. It could be said, with reference to seawater volume, that one fish in a home aquarium is one fish too many when compared to the overall gallonage available to reef fish. Of course, technology and knowledge of husbandry make the difference.

So corals are generally used to stability, though in some areas temperature may change significantly but slowly. In the home aquarium temperature, if permitted, will change quickly and by a large amount. During the day, the temperature may climb significantly as the aquarium seawater is influenced by summertime temperatures and/or by halide lighting etc. Then night arrives, the lights turn off, the air temperature falls, and the seawater temperature falls relatively quickly as there is only a small volume. This danger is more real the smaller the aquarium is. The nano reef aquarist has to be particularly on guard. All aquariums of whatever size are subject to the problem to a greater or lesser extent. So what to do about it?

The ‘usual’ temperature setting for a marine aquarium is 75, 77 or perhaps 79 Deg F, or somewhere in between. The corals and fish etc function at these temperatures without problem. However, the temperature increases and decreases generated in an aquarium can put reef inhabitants under stress. This stress will continue for so long as the aquarium temperature variations continue, and the greater the variation the greater the stress. This is not something the aquarist will wish his livestock to be subjected to.

If the temperature variation is more than 2 Deg F, in summer or winter, between the coolest point at night and the warmest point during the day, then the aquarist should raise the temperature setting of the heaters to 80 Deg F. This is a safe setting for corals and fish etc. This then means that the warming of the aquarium seawater by outside influences will take longer. When those influences are gone, the seawater will not have to cool down so far if it has heated up at all.

This does not mean that the [tag-ice]aquarium heater[/tag-ice] can simply be turned up. Doing so would be the opposite to what is being attempted. The heat level should be increased slowly, 1 Deg F each day as a maximum. It would probably be better to allow 48 hours or even more per degree of increase.

Nor does this mean that the need to monitor temperature variation can be abandoned. The aquarist in a cool zone may normally never see aquarium temperature climb above the norm, but may use halides. A day may come when the weather is particularly warm and then the rise could occur. In this unusual occurrence the use of a cooling fan may be all that is needed. Aquarists in warmer climates may always have temperatures over 80 Deg F. In this case the use of a seawater cooler (chiller) is the obvious option. There’ll not be any heating cost so cooling is a practical option. At an 80 Deg F cut-off setting the cooling device will work over shorter periods and thus cost less to run. The aquarist who has cool winters but warm summers may have no problem over the winter but may see excessive temperature rise in summer. If the excess is small, a degree or so, then fans may be able to cope. If the rise is greater, then a cooler may need to be used. Again, when the cooler is in use the heaters won’t be, helping to control running costs.

There is another good thing that can occur when the temperature setting is raised. Increased temperature increases the metabolism of the creatures of the reef. Provided adequate food is available, the tiny creatures on and in the reef (and DSB (deep sand bed) if there is one) will breed and multiply more rapidly. So there is more activity. Also, the fish will be more active (and hungry).

There is a danger. As the temperature increases the amount of dissolved oxygen decreases. However, in a properly designed and stocked aquarium there should not be a problem. In a poorly designed and/or badly overstocked system there could be. The great majority of aquarists I’m sure should have no fear, but just be aware.

As mentioned earlier, electricity costs could be affected. The aquarist who seldom sees a temperature rise above 80 Deg F will have the heaters switched on for longer periods. The aquarist will have to decide what the probability of excessive temperature variation is and act accordingly. The aquarist in a warm zone who sees temperatures above 80 Deg F may see an electricity saving. If the cooler cut-off temperature has been raised, the device will use less electricity. The aquarist who has cool winters and warm summers – winters will not make any difference, and if temperatures rise in summer then the heaters will switch off to be replaced perhaps by the running cost of a cooler. Hopefully, the cooler will not have to work too hard and costs may prove reasonable.

This simple method of achieving aquarium temperature stability, or at least increasing it, moves the aquarist nearer to the prize, all things being equal. The prize is a vibrant and healthy reef.

( * Source: Borneman E. H. Aquarium Corals.)

There are places in the world where it is always or mostly warm (coral reef areas are an obvious example). In the summer the weather can be warm and very pleasant where I live. Well, no problem with that says I! It can be a problem, though, if you keep a [tag-ice]salt water aquarium[/tag-ice].

A tropical salt water aquarium is designed to run at a given temperature, usually between 75 and 80 deg F. This temperature is maintained by heaters. Here’s the scenario – the summer has come with its increased temperatures, so the heaters are not working anywhere near as hard, sometimes not at all. The equipment on the aquarium hasn’t changed, so there is heat going into the water from pumps and power heads, and in addition the water is being warmed by the lighting. Even fluorescent tubes have this effect, but nowhere near the effect that halides have. In addition, a few aquarists have glass covers on their tanks to reduce evaporation and/or prevent inmates jumping out. So the sum total is seawater that is at a temperature above the design temperature. A little above is not too bad, but the temperature can rise too much. This causes reduced oxygen, and the heat can stress the tolerance of corals and other livestock. So we don’t want that.

Right, we could remove cover glasses, and use fans etc to help control the seawater temperature. Some methods work fairly well.

Consider how often the [tag-tec]aquarium temperature[/tag-tec] is likely to rise above the design temperature. This is fairly easy, the weather patterns (temperatures) are known to you. If the period of likely excessive temperature is considerable, consider purchasing a chiller. Remember that when a chiller is operating, the heaters will not be, so electricity usage shouldn’t be increased by the chiller.

A chiller is a device specifically designed to cool seawater temperature. The devices I am talking about are not modified beer chillers etc, but equipment specifically designed to cool overheating aquarium seawater. The contact areas between the equipment and the seawater are of special materials, so the seawater will not be adversely affected.

An [tag-tec]aquarium chiller[/tag-tec] is not for everyone, as they are expensive and fairly heavy on electricity. So there needs to be a good case, that is, the knowledge that they will be reasonably extensively used, before a purchase is made.

They are easy to obtain and come with clear instructions. Be sure that the chiller has the capacity to deal with the net gallonage in your aquarium. When connecting to your system, be sure to adhere to the seawater flow rate recommended by the manufacturer, so the seawater has time to cool. The usual case is that the heaters are set to the design temperature, and the chiller thermostat is set to 2 or 3 deg F above the design temperature. The seawater heats up, the heaters stop heating, the chiller thermostat detects the heat rise and, well, yes, the chiller starts chilling.

So there we are. Overheating problem solved.

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.