The substrate heating
With a substrate heating you promote the growth of your aquatic plants enormously by creating a water circulation in the substrate, which washes nutrient-rich water directly to the roots. A substrate heating consists of a long heating cable which is laid in curved lines on the bottom panel of the aquarium. The water heats up directly at the cable and rises upwards. Cooler water starts to flow between the cable loops, creating a water circulation in the bottom area which permanently washes nutrient-rich water to the plant roots. Only very fine substrates (fine sand) might prevent a sufficient water circulation for a substrate heating. In this case heat is very likely to become trapped at the bottom, which is not ideal. That’s why undergravel heating cables are only suitable from grain sizes of around 0.8 mm onwards.
A substrate heating is not meant to heat your aquarium water, it only serves as “micro circulation” in the bottom area. Therefore the wattage of the undergravel heating cable is significantly lower than that of heaters. You can read how to install a substrate heating here: Instalacja Wyposażenie techniczne .