Red mangrove would probably be the best choice, but one thing to consider is mangroves can become vary large in time. Another thing to consider doing is spraying the leaves with freash water to simulate rain in the tropical areas there from, thats how they get most of there water. They do a well job of filtering out nitrates out of saltwater, there roots do well in poor soil conditions and high salinity making them hardy, but they do best in miracle mud but may servive in just sand. They like lots of light that they adapted to in the tropics. Also a fan to blow air around them will aid them. In my opinion they are a nice looking tree.
Had 50 of these growing in a few inches of sand.
About to set up a small cube just for a few of them.
They are fun to grow but don't expect to use them for nutrient control
They're growth is much too slow.
As mentioned above you will need to spray the leaves and in time you will need to prune them.
Here's some really good info. Mangroves,aquariums and you! - Macroalgae & Plants - Nano-Reef.com Forums