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How to keep your aquarium cool in summer

Summer temperatures may be a blessing for those of us who love the sunshine, but for fishkeepers, it also calls for extra caution as we must make sure that our aquatic friends are feeling cool and comfortable. Whether you’re caring for a marine tank with tropical fish and corals or a freshwater aquarium that is kept cool year-round, maintaining the temperature of your tank is imperative to creating a balanced underwater ecosystem, and when heat waves come around, this task is made more difficult.

The effects of rising temperatures on fish are different for each aquarium so it’s important to know the signs of overheating, as well as how to combat the issue in order to create a safe home for your fishy friends. In this blog, we are going to take you through everything you need to know on how to keep your fish tank cool and all the signs to look out for, no matter if this is your first or fourth time caring for a tank during the high temperatures of summer.

What happens if my tank is too hot?

When the temperature of your fish tank increases, two things happen as a consequence. Firstly, the higher temperatures will increase the metabolic rate of your fish, causing them to breathe more quickly and need more oxygen. Secondly, the water’s capacity to hold oxygen will decrease, making it harder for the already heavy-breathing fish to get the oxygen they need. These two consequences of overheating water can have disastrous consequences, particularly when fish become stressed as a result, as stressed fish are more susceptible to illness.

Though these issues can impact all species of fish, and you should be extra vigilant in your fishkeeping care duties in summer, some types of fish are more at risk than others:

Marine fish and inverts are significantly more tuned to their natural environment than freshwater fish. This means that they are even more demanding and need a stable temperature range to thrive, so they might need to be monitored more carefully during the summer months because, ideally, they would have no temperature changes at all for a completely balanced ecosystem.

Tropical fish may seem easier to care for in summer due to their pre-existing need for warmer water, but in actual fact they are still susceptible to illness when their ideal temperature range is exceeded. As such, in summer it’s important to make sure that the maximum temperature they require is not pushed too far, especially during summer heat waves. If taken beyond the maximum temperature, your fish may become stressed and this can lead to outbreaks of disease and could end up being fatal.

Signs your fish are too hot

If you’re not sure how your fish are coping with the heat, there are a few signs you can look out for. On hot summer days, if you find your fish at the top of your aquarium gasping for air then this means your tank doesn’t have sufficient oxygen for them. You may also find their gills moving faster, which is another way to know if your fish aren’t getting enough oxygen in their tank.

While relying on these visual signs of distress is good for spotting a problem after it has arisen, we also recommend adding a thermometer to your setup to help you constantly monitor the tank temperature. Capable of providing you with an accurate view of the temperature of your tank at all times, water thermometers can help you catch increases in water temperature before the spike impacts your aquatic friends. This Aqua One glass stick thermometer is easy to install, simply stick it inside your tank where you can see it and it also comes with an easy-to-read green line that tells you the ideal temperature for your tank. This guide will help you to know when your tank is starting to get too hot during summer so you can keep your fish feeling comfortable and happy.

Aqua One Glass Stick On Thermometer

Aqua One Glass Stick On Thermometer | £4.30

How do I keep my fish tank cool?

There are a few ways that you can keep your aquarium cool during the hot summer months. Ranging from quick tricks you can use to help reduce temperature quickly, to long-term solutions that require more investment but are safer for your tank inhabitants, we’ve detailed the three best options to try below.

1. Keep the tank environment as cool as possible

The first option is easy to do, simply turn off your aquarium lights and ensure the tank's surroundings are cool by trying a room fan or an air conditioner in the same room as your aquarium. If you have T5 lights or metal halide, these lights can get very hot and cause temperatures in your tank to rise, so turn them off for longer during the day. Or in the case of planted and reef aquariums, limit the number of hours the light is on to help reduce heat generation.

2. Invest in an aquarium cooler fan

A cooler is a fan which sits on top of your tank and cools the water temperature by increasing the evaporation rate, however, due to this you will need to top your tank water up more often. Coolers will be more reliable and easy to use during those summer months to help see your fish friends through until autumn when temperatures start cooling off again. This JBL Pro temp cooler is perfect for cooling off your freshwater or marine tanks by up to 4°C with the help of cross-flow fans.

JBL Pro Temp Cooler x300

JBL Pro Temp Cooler x300 | £52.92

3. Get an aquarium chiller

A chiller is another great and reliable option for your tank during those summer heatwaves. It’s placed under the water, unlike a cooler, and will filter the water through its system to chill it down to a safer temperature before pumping it back into the tank. Try this D-D DC300 aquarium chiller that can have as much as a 5°C temperature drop, making it a great way to combat those hot summer days. If you have a heater for the winter months, you can also make controlling the temperature of your tank year-round that little bit easier by also installing a D-D Dual Heating & Cooling Controller.

D-D DC300 Aquarium Chiller

D-D DC300 Aquarium Chiller | £449.99

How to cool an aquarium fast

It’s very important to note that you should never drop the temperature of a tank too rapidly otherwise it may cause harm to marine life. A drastic change in temperature can trigger an onset of ich disease or other parasites, so be aware that cooling down a tank too quickly may do more damage than good. We recommend not lowering the temperature more than 2°C or 3°C in any 4-hour period.

However, if the temperature is at a fast incline and you’re worried about the inhabitants there are some methods you can use to cool your aquarium quickly and easily.

Put a bag of ice in your tank - You can try putting a floating bag of ice or cold water in the tank to gently lower the temperature. Avoid putting ice cubes directly into the tank, always make sure they’re in a separate bag unless you're using de-chlorinated water.
Perform small water changes - You can also perform small water changes by adding slightly cooler water to your tank. We recommend changing the water at about 10% - 20% of the tank at a time so as to not bring harm or stress to your fish by dropping the temperature too fast.
Move your tank into the shade - Another quick way to cool off your tank is to simply move the tank into the shade or out of direct sunlight in your home. If moving isn’t an option, you can also draw the curtains to block the sun from your fish tank.

Keep your aquarium cool with Aquacadabra

Here at Aquacadabra, our expert fishkeepers are always on-hand to help you learn everything you need to know about looking after an aquarium, as well as supply you with what you need to give your aquatic friends the best home possible. If you need more advice on how to keep your tank cool during summer you can contact our friendly team for advice.

You can also read through our guide on what temperature your fish tank should be for more help, or browse through our helpful aquarium temperature collection and give your aquarium the thriving underwater ecosystem it deserves.