Heating and cooling
The right temperature for your aquarium dwellers
Did you know that most tropical waters are “only“ 25 °C, even when the air temperature is above 30 °C? Only large, slow flowing rivers and lakes are an exception because they are less shaded by trees which means they are heated more by the sun. The oceans, of course, are a world of their own.
Thus most fish and plants are most comfortable in your aquarium at 24-26 °C and only a few fish, such as the discus fish prefer temperatures of nearly 30 °C. Many shrimp species on the other hand prefer cooler water and don’t like hot summers at 28 °C water temperature. They do best when small fans are used to cool the water. ( Cooling ).
Depending on where you live, your room temperature might be below your desired water temperature. Only in summer and in tropical countries is heating not required. Heater thermostats heat up your water to the pre-set water temperature then switch themselves off. This way your required water temperature is constantly maintained.
You can, of course, run your aquarium with tropical fish without a heater when your room is warm enough to CONSTANTLY keep water temperature between 24 and 26 °C. From experience, without a heater, fluctuations occur, which your aquarium dwellers do not experience in nature and, which they do not appreciate. An automatic heater thermostat will help you to keep the desired temperature at a constant level. You set the temperature on a dial on the top of the heater and it will always heat when this temperature falls below this set temperature. Make sure when inserting the heater that there is a good flow around it to prevent heat accumulation, which would lead to it switching itself off instead of heating the aquarium. Select your heater according to your room temperature. The important factors for the choice of heater power are the size of your aquarium and the temperature difference between room and desired water temperature, the so-called ∆T.
For larger aquariums from 250 litres upwards experienced aquarium owners use two heaters instead of one, as they only reach the required water temperature together. In the event of a fault (which is very rare – but like with the safety instructions in a plane, we have to draw your attention towards it) one heater prevent the other from causing the unwanted death of the fish.
Please don’t select a too strong heater size to be on the “safe side”! This would lead to the switch on and switch off periods of the heater being very short and switching back and forth too often. This permanent on/off behaviour shortens the service life of any heater!
It is NOT the task of undergravel heating cables to heat up your aquarium water to the desired temperature but solely to create a water circulation inside the substrate to improve the nutrient supply for the plant roots. Therefore a substrate heater is ONLY a tool for the care of plants (see Substrate ).
An insulation of your aquarium with a foam underlay and possibly also with a thermal insulation on both sides and the rear pane will help you to save energy costs.
As already mentioned there are aquarium dwellers, such as shrimps which prefer lower water temperatures of 22-23 °C and tolerate high temperatures of 28 °C only for a short time. But a lot of tropical fish species and aquarium plants in particular also feel uncomfortable at high temperatures. Plant growth can even stagnate noticeably because of too high a temperature! JBL provides you with an inexpensive and effective cooling solution which you can easily install in your aquarium:
Fan units (various lengths available) create an air flow at the water surface which leads to an evaporation cooling process (similar to your sensitivity to the cold when you ride a bike). This way you can reduce the water temperature by approx. 4 °C. With a thermostat ( JBL CoolControl ) you can have your fans switched on automatically in case your set temperature is being exceeded.
With the help of a water thermometer you can easily see what’s happening to the temperature in your aquarium. You can choose between various versions and a thermometer which you can stick to the outside of the glass pane: Thermometers & hydrometers .