Jbl Sansibar River 10Kg Ideal substrate The substrate is an important part of the aquarium interior because a lot of animals dig in the ground to search for food. The plants also need a safe hold and have to absorb the food in the ground through their roots. Digging fish definitely need a substrate which is not sharp edged. Undergravel heating can only be recommended for medium fine to coarse substrates because water circulation cannot really build up in very fine substrates. Use Rinse the substrate with tap water to remove any abrasion caused in transit. Put substrate on the nutrient substrate JBL AquaBasis to promote the plant growth for for vigorous root development approx. 6 8 cm.