Frag tank

[bling_bling466]

Well I've been think of starting up a frag tank with a 20g long and Ive got an old coral life 65 skimmer I was going to put live rock on the bottom with egg crate about 4-8 inches above. Is it possible to skim to much as I was going to use my old water for my tank for nutrients as there won't be any fish. It will be mostly sps and some Lps. With no sand bed. Ive also got an old 36" stand any shallow 36" tanks out there?