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Cooling Your Aquarium In The Summer

11 July 2020


Are hot summer days dangerous for my tank?


As of the end of June, we entered the wonderful season of summer. But whilst it may be lovely to have an unexpectedly hot sunny week, it’s best not to let those hot periods take your fish by surprise.

An overheated aquarium for prolonged periods of time can be harmful to fish (if not, disastrous) for many reasons. Fish are affected differently depending on the aquarium type. For example; tank size, tank depth, tank surface area, fish population, water quality, water circulation, water surface agitation and ambient room temperature are all factors which change the outcome of a period of hot weather. Short heat spells are usually not a reason to worry, but obviously longer heat waves can cause issue.

Higher temperatures can reduce the much required dissolved oxygen levels within the water. With the body temperature of the fish increasing alongside their metabolism rate and activity levels, we have a double problem. The tank issues are magnified within a saltwater aquarium because saltwater already holds less oxygen than freshwater of the same temperature.

Fish may show signs of stress during a spell of warm weather. An example of this is rapid gill movement or gasping at the surface of the water more than normal. Algae may have growth spurt and the bloom of heterotrophic bacteria may give your water a cloudy appearance. Of course, the immune system of the fish may become lowered when they are under stress.

Also, take note that in extreme cases, the filtration system may become compromised, causing it to become much less effective, thus increasing ammonia and nitrate to rise to a potentially toxic level.



What can you do?


Before reading this section, please note that it is unsafe to reduce the water of your tank more than 2 degrees in a 6 hour period as sudden changes in temperature can potentially shock the bodies of your fish and cause harm to them.

It’s easy to forget that aquarium lights give off a lot of heat! So turning off the lights within the aquarium can really help to reduce the temperature of the water. It is worth noting low wattage LEDs also give off smaller levels of heat. Remember, direct sunlight will cause the water to heat very quickly too, so ensuring your tank is placed in a shaded cooler part of the room is vital to surviving a heat wave. Remember to close the curtains (to block the hot sunlight) but also open the window to encourage those cooler breezes to circulate the room.

Installing an airstone is also great advice as it improves the dissolved oxygen levels throughout the water- especially handy when the hot weather is reducing those oxygen levels.

Another idea for cooling down water is floating a small bag of cold water in the aquarium to gently cool the water. Some people may drop a cube or two of ice into this water bag too. Just be careful not to change the temperature of the tank too quickly.

Turning the thermostat off is something you may have been advised to do when cooling down your tank, but we feel it is safer to turn the temperature down rather than unplugging your system completely. The reason we advise this, is because there is a risk of forgetting to plug the heater back on and this sudden drastic drop in aquarium temperature can be shock the bodies of your fish and even trigger the onset of ich or other parasites.

With the aquarium top unopened, a cooling fan or domestic fan can be used if positioned safely with cables safely out of the way. The circulation of air will blow heat away from the surface but bar in mind it will also increase evaporation.

Doing a water change with cooler water than what is in the aquarium already can work safely if it is done in small quantities. So a 20% water change with water that is around 5-6 degrees cooler than the original tank water should ensure the temperature only drops at a safe rate of around 1 degree.

Polystyrene can be your friend! Insulation is a two way system so polystyrene can be used to cool down your aquarium by helping to keep the cold inside and the warmth outside. This can be created at home with some tape and polystyrene tiles around all sides of the aquarium.

A more perfect and worry free solution is to install a chiller. This may cost more, but after extensive research it shows great results with regards to cooling down an aquarium safely. There are plenty of places you can buy chillers from. Get in touch with us to find out more.