How much sand, gravel or aquasoil to buy for your tank, from its footprint and the depth you want.
Two to three centimetres is plenty in a tank with no rooted plants; five to eight gives root-feeders room, and a bed that slopes deeper at the back reads as natural. Sand suits corydoras and burrowing fish, gravel is forgiving and cheap, and aquasoil feeds plants but costs more and buffers the water soft. If you run an undergravel filter you need gravel of a suitable grain. Work out your water volume with the volume calculator and start plants with beginner aquarium plants.
Multiply the footprint by the depth you want. This calculator turns that into litres and kilograms to buy, with a 10% margin. Aim for 2 to 3 cm without plants, 5 to 8 cm for root-feeders.
Roughly: sand 1.5 kg, gravel 1.6 kg, aquasoil 0.9 kg per litre. Real bags vary, so treat the weight as a buying guide.
About 2 to 3 cm with no rooted plants, 5 to 8 cm for plants that feed through their roots. Buy about 10% extra for slopes and settling.
Volume = footprint area × depth. Weight uses typical bulk densities (sand ≈ 1.5, gravel ≈ 1.6, aquasoil ≈ 0.9 kg per litre); real bags vary, so buy about 10% extra, especially if you want a slope or a deeper planted bed at the back. As a rough guide, aim for 2 to 3 cm in a non-planted tank and 5 to 8 cm where you want root-feeding plants.