Full max, realistic waters job is to give the illusion of having water, not to substitute for it, I think I know what you mean with the half inch depth, but you only really need the 1/8 depth because you only need the small film on top, it makes it look like the pond is much deeper, instead of blowing 30 bucks of realistic water on a lake you can just poor a film and make waves or something so you cant see the bottom, and even if you can it will still be ok.
You have to add the layers on, one at a time anyways, so try adding the 1/8 and see if your happy, if not continue to layer untill you are!
Good luck and have fun!!!