So here it is again, the summer heatwave. Some of us are glad of the chance to be outdoors all day again, while others are simply drooping in the heat. The temperatures at home are rising steadily. Without air conditioning or a fan, the heat can be a real challenge.
If you own an aquarium you’ll be asking yourself what effects the heat has on your aquarium and on your fish. As soon as the room temperature is higher than the temperature you want in your aquarium, the room stops cooling the aquarium and has a heating effect on it instead. Experience shows that the room temperature can reach 30 °C. Even if the temperature is "only" 28 °C, the lighting, the pumps used and a closed aquarium cover will drive the thermometer up further.
How can you bring the temperature down?
It is well known that most freshwater fish can withstand temperatures of 30 °C for a few days without any problems. The animals get used to it slowly, as the temperature rises slowly over several days. However, this is not the case in a marine aquarium. Here you need to take the first precautionary measures from 28 °C. But which ones?
As is so often the case, the internet is full of specialists, often on social media, making recommendations. Take these suggestions with a grain of salt and be a bit discerning. Here are a few classics to avoid at all costs:
- Ice cubes
- Cooling packs
- Water change with cold water
Don't do it. The temperature will drop rapidly, but only in the short term, and it will unnecessarily stress your aquarium inhabitants. It’s better to look for long-term solutions. Here are some helpful tips to save a few °C without stressing your fish:
- Avoid direct sunlight by closing curtains or blinds.
- Open the aquarium cover so that heat can escape, this way evaporation provides a cooling effect (approx. 1-2 °C).
- Reduce the lighting time by 50 %. Because light makes heat, even your much loved LEDs get hot when continuously operated (approx. 1 °C).
- Increase the oxygen content in the aquarium by using an air pump for more surface movement and more active oxygen input. As the temperature rises, the oxygen saturation level in the water drops. This will help counteract this.
- Create more flow in the aquarium. Point the filter outlet towards the water surface. The strong surface movement increases the oxygen input. This in turn lowers the temperature through evaporative cooling.
- Switch off non-essential technology such as underwater lighting, substrate heaters and any superfluous pumps not in use for filtering or necessary flow generation.
What can you do if none of these tips help?
The measures listed above may not be enough to get your aquarium through long periods of heat, but they’re still worth doing. If you need to intervene further, an effective circulation cooler (water chiller) is reliable, but also very expensive and high on electricity consumption. This usually makes them unfeasible.
We recommend cross-flow fans (also called coolers) that you can place on your aquarium. They provide an even and wide-ranging air flow onto the water surface. The resulting evaporation brings the desired cooling effect of 2-4 °C. Please stay away from the classic PC fans, which are often suggested as a DIY solution. They don’t create an air flow over a wide enough area on the water surface, they can’t be directed and they’re not suitable for installation near water. If water splashes on them they’ll blow your fuse. In all, we strongly advise against them! The last thing you need is for your aquarium to be without power or for you to be injured.
You can mount the JBL PROTEMP Cooler x200 (gen 2) and the larger version JBL PROTEMP Cooler x300 (gen 2) on the edge of the aquarium with a stable bracket and align them at an angle to the water surface. The controller JBL PROTEMP CoolControl , which is also available, allows you to set the temperature you want and the fans will automatically switch off when it’s reached.
Stay cool!
As we mentioned, a few days in the aquarium with temperatures of around 30 °C are not initially a problem. It takes weeks for the stress to become a danger for your fish and harmful for your plants. So stay cool in short heatwaves.
It’s generally advisable to reduce the feeding to a minimum in very high temperatures, to reduce the oxygen demand of the fish and the water pollution. We also recommend you regularly keep an eye on the fertilisation parameters iron ( JBL PROAQUATEST Fe Iron ), nitrate ( JBL PROAQUATEST NO3 Nitrate ) potassium ( JBL PROAQUATEST K Potassium ) and magnesium ( JBL PROAQUATEST Mg Magnesium Fresh water ). Why? Because high temperatures often cause plants to reduce or even stop their activities. Make sure you also adjust their fertilisation for this period.
Measure the temperature ( Thermometer ) and the oxygen content ( JBL PROAQUATEST O2 Oxygen ) regularly. This way your fish will survive and thrive in the summer.
The cylinder fan wheel of the Cooler 200X or 300X moves a large amount of air to ensure sufficient evaporation and thus cooling on the water surface. As with a room fan, it makes a noise, but it’s bearable.
