02-14-2019, 10:07 AM
A soil substrate with a cap of simple gravel or pool filter sand gives excellent results and is very inexpensive. This is the basis of the Walstad method, a.k.a. natural planted tank, El Natural, etc. There is a whole forum devoted to it at APC: https://www.aquaticplantcentral.com/forumapc/el-natural/