How to Cool Your Aquarium

With temperatures in the UK reaching 33deg C. this week, it looks as though the summer may have finally arrived here in the UK! These temperatures bring with it the ‘hot topic’ (sorry) of how to deal with elevated temperatures in our fish tanks. This article will outline the problems associated with impact on our livestock; with suggestions how to manage this problem.

There are primarily two issues associated with our aquariums overheating:

1 - Reduced Levels of Oxygen

As water increases in temperature, its capacity to hold oxygen decreases. To compound this issue, as fish are cold blooded, their metabolism increases in line with water temperature increasing the quantity of oxygen that is required. This two fold issue often becomes apparent on hot summer days when fish can be seen gasping at the top of an aquarium (or pond) – and can lead to losses of livestock.

2 - Increased Stress

Our livestock has evolved over many millennia to be adapted to the specific geographical regions from which they originate. Fish from the Amazonian rainforests will be more adept to higher temperatures than fish from the foothills of the Andes where the water is cool. We are all aware that our tropical fish need heaters to ensure the minimum temperature that they require is provided, from the opposite perspective we need to be aware that a maximum exists – and that when taken beyond this maximum temperature, stress will be caused leading to outbreaks of diseases and loss of livestock.

Marine fish and inverts are significantly more tuned to their natural environment than freshwater fish. As such, they are even more demanding, requiring an extremely stable temperature range – ideally with no variation at all! An increase in temperatures of just a few degrees can lead to the loss of sensitive invertebrates and corals, which is why global warming is such a threat to the world’s coral reefs.

Now that we know the problems associated with our fish tanks overheating, let’s look at how to address the problem.

The environment around our fish tank

We all get uncomfortable when temperatures rise, particularly here in the UK where few people have air-conditioning at home! Opening windows and drawing curtains can help to keep things a little cooler – but only a little unfortunately.

Changes to the fish tank

It’s possible to make a few changes to our fish tanks to help reduce temperatures temporarily. If you have a hood or lid, this can be opened to help heat dissipate (assuming  you don’t have fish that jump!). If you have a sump, open the cabinet doors and position a fan to blow air around the cabinet.

Lighting systems often produce a lot of heat – particularly metal halide lighting. Options to address this include reducing the number of light tubes you use, or the length of time that the lighting is operational. Obviously this depends upon your livestock, if you have corals and inverts that require high levels of lighting, this may not be possible.

Over the last few years, LED lighting has become very popular. One of the benefits of this approach is that LEDs generate very little heat. Replacing Fluorescent Tubes or Metal Halide lighting with LEDs will significantly decrease the amount of heat that your fish tank is exposed to (and will also provide you savings on your electricity bill) Arcadia Eco-Aqua LEDsare an ideal replacement for Metal Halide lighting – and TMC’s AquaRay Solid State lighting is extremely popular.

A final option is to reduce the amount of electricity that is used within your aquarium. Every electrical item in your aquarium will generate heat, so reduce the number of pumps that you have operating, or replace them with lower wattage pumps. It is appreciated however, that this may not be practical.

All of the methods outlined above can contribute to a short term solution, however they are often impractical and should not really be relied upon (other than the LEDs which will make a difference).

A practical and long term approach to overheating

There are a number of products available, to suit all budgets, the help keep temperatures under control in your fish tank – with pro’s and con’s associated with each.

Cooling Fans

Aquarium cooling fans are available from a number of manufacturers including Aqua Medic, Hobby and Tunze. They are either fitted to the top glass of the aquarium or suspended above; and direct a stream of air onto the aquarium water’s surface. When using cooling fans you’ll need an aquarium with an open top.

Cooling fans are great at reducing the temperature of your fish tank by several degrees, which may be all that’s needed on a hot sunny day. They’re also competitively priced, starting from around £35 – providing great value for money.

There are however a few drawbacks associated with cooling fans. Firstly, they significantly increase the amount of evaporation that takes place in your tank. On a Juwel Vision 180 I used a cooling fan and the tank needed topping up daily. This is fine if you’re there to do this, however if you’re on holiday for a week or two and relying on a neighbour, you could run into problems.

Another issue is that cooling fans are not thermostatically controlled. As such, they’re either switched on or off, unlike your heater. As such, you’ll need to be available to switch the cooling fan on, and if the ambient temperature drops whilst your cooling fan is still running, you may find the fan competing with your aquarium heater.

Aquarium Chillers

The alternative approach to cooling fans is the use of an aquarium chiller. Before we discuss how they work and the pro’s and con’s in depth, lets get straight to the main issue when we refer customers to aquarium chillers – ‘ouch that’s expensive!’ We can’t deny this, unfortunately it is true! We stock chillers by D-D, Aqua Medic and Teco; and for the smallest units there isn’t any change out of £300. Aquarium chillers however offer the only reliable and practical long term approach to keeping your aquarium’s water within it’s safe range.

In overview, the great majority of the chillers that we sell include coolants and work in a similar manner to your household fridge. Water is passed through the chiller where it is cooled by several degrees through heat exchange, before being returned to the fish tank. As such, the chiller needs plumbing into the aquarium, and a water pump will need to be used to circulate the water. Ideally, this will be clean water, so it’s best practice to include a chiller as part of your filtration system.

So let’s look at the benefits of using a chiller:

Aquarium chillers use coolants that exchange heat from the water that passes through them, without increasing evaporation rates – therefore keeping water conditions stable at all times.

Chillers are thermostatically controlled. Always there, always ready switch on automatically when needed and most importantly, switch off if no longer needed. Aquarium chillers provide total peace of mind and ensure that water conditions remain constant throughout the year – whether that be an uncharacteristically warm day in March, or cold dull day in August.

If you use a chiller, you won’t have to compromise on lighting and water movement – the chiller will compensate (assuming you use an appropriately sized chiller that is!).

So let’s get back to the main issue, price. Yes it’s true, aquarium chillers are expensive. However, they offer the only truly practical method of maintaining stable water conditions within your aquarium, without compromise. If you have sensitive livestock, such as corals and invertebrates, knowing you have a chiller installed on your aquarium will help you enjoy the warm sunny days of summer; without constantly checking your aquarium’s water temperature and worrying about losing livestock. If your budget allows, an aquarium chiller is a sound investment for both your livestock and your own peace of mind.

In summary, aquarium fans do provide an immediate solution for addressing elevated water temperatures, and if you have a limited budget they are a great help. If possible however, an aquarium chiller will provide reliable long term solution, helping you to manage water temperatures even if we have a really hot summer.