The only way I can think of doing this is having two different levels in the tank, with a short divider inbetween them to stop the mud falling down into the lower level.
I've heard of people making mangrove diplays before but I have never actually seen one. You would have to choose the naturally occuring fish though. I don't think those fish you mentioned would be happy in this kind of biotope.
Why don't you just get a hang-on fuge for the mangroves?