You dont really need any more unless you want a deeper bed.. I personally like really deep sand, so i would add more sand. But i wouldnt add live sand. Your sand is already live, so you would be better off just adding plain dry sand...it will become live in a couple months or so. Dont add it all at once though...i'm thinkin you only do like 1 inch at a time every 2 weeks or something like that.