The substrate heating
The substrate heating washes nutrients to the plant roots
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: Installation technical items .
What do I have to bear in mind when installing an undergravel heating cable?
First of all, there is the timing: the installation is only possible with an empty aquarium. Try to restrain yourself if your pet shop assistant only recommends a undergravel heating cable after you have bought your entire setup equipment from him.
BEFORE you lay the cable in loops at the bottom of your aquarium, consider which areas you will plant. The heating cable only is useful in these areas.
There is also another factor: you will probably place a long-term plant nutrient substrate ( JBL PROFLORA AquaBasis plus ) above the heating cable. Later, when you clean the ground with a substrate cleaner (gravel cleaner: JBL PROCLEAN AQUA EX 10-35 ) and plough the substrate to suck out the dirt, you won't want to pull out the nutrient substate again or get caught in the undergravel heating cable. SO only place the heating cable and long-term nutrient substrate in the planted areas.
The undergravel heating cable consists of a cable part that does not heat up and a part that does. The "cold" cable part should end where the cable enters the substrate.. Only the part of the cable under the substrate needs to heat up. You can identify the transition from the part that remains cold to the part that heats up on the JBL undergravel heating cables ( JBL PROTEMP b III ) by the black marked part of the heating cable.