Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Vals are fine in sand, but add fertilizer tablets or water column ferts. I find they grow better in a richer substrate. I use one of the montmorillonite clays, Safe T Sorb or similar for most of my tanks.
Easiest way to get started with ferts is to start with one of the bottled products. Get used to dosing, and get some idea as to how much ferts your tank is using.
Then you can make the call if you want to be more economical and buy dry ferts to make the solutions yourself.
Seachem Excel or similar (active ingredient Gluteraldehyde) is a reasonable source of carbon for many plants, but Valisneria does not seem to like it at higher doses. If you decide on a liquid carbon source only dose at the lower end of the suggested dosing.
Will that many Firemouths be OK in that tank? It is a rather compact shape, so all their territories will be within sight of each other.