ah, I misunderstood. I thought you meant setup a saltwater paladarum with mud and such to make something like a brackish marsh.No - there is no reason you couldnt take a 'big' (up to the OP's definition) - stack up rock - so water cascades down the sides into the bottom half. Whats not clear is whether a sump in an issue. Ie if. was going to do it. - I would have an overflow set at 1/2 of the tank. Mangroves - as already mentioned, etc etc - could be used. It could be cool IMHO