Most aquarium fish come from tropical waters and need water temperatures between 22 and 30 °C. In community aquariums with fish/invertebrates from different regions, a water temperature of 24-26 °C has shown to be effective. 30 °C is only suitable for some fish breeding (e.g. discus fish). Many shrimp species come from cooler waters and do not tolerate temperatures of 25-30°C.
The water temperature should be set with a "regulated heater" which regulates the temperature automatically. For this purpose, there are rod-shaped heaters which are fixed in the aquarium (JBL ProTemp s) in various wattages and external heaters/in-line heaters which are integrated in the water-returning hose of an external filter (JBL ProTemp e) in two wattages. The advantage of external heaters is that it is one less product to be placed INSIDE the aquarium and the distribution of heat in the aquarium is more even. In addition, the digital display of the external heater always clearly shows the current water temperature.
Undergravel heating is NOT used to set the water temperature. An undergravel heating cable ensures a better flow of water through the substrate of the aquarium, as the heated water at the heating cable rises and colder water flows into the areas between the heating cables. Thus nutrients are flushed to the plant roots and ensure optimal plant growth. Undergravel heating cables must always be supplemented by a "main heater" (JBL ProTemp s or e).