go to menards they have a black blasting grit. works like black diamond, or sounds like it does.
I have it in three tanks
--clean it well, really well.
--when you first put it in it will have a grey/brown layer on top, that will disappear as snails/fish mix it up/
'bout $5.00 a 50lb bag
20L My Other Tank: OEBT Shrimp
40B Inlaws Tank: 2 goldfish
75 Main Tank w/ sump: 5 Glossolepis pseudoincisus, 5 Melanotaenia boesemani, 10 Melanotaenia praecox, 5 Melanotaenia lacustris, some cories, a bn pleco and rainbow fish fry