it won't be a natural environment. the fish you will purchase don't live in habitats that have mangrove trees in them. mangroves are in shallow, marshy areas. also, you'll need to stick the top out of the water. you will have to have either a super deep sand bed, or a super shallow tank to accomplish your design. you'll also need to hang a better light over the plants.
what i would do is add a refugium next to your display. use the mangroves there, and add some other, ornamental algae as well.