Sea shell flooring?? Do you mean crushed coral? Or crushed shells, or.. what? Do you plan to at least have some sand?
In the event that you plan to have just crushed coral and no sand, may i give you a warning?
Crushed coral, and "seashell flooring", due to their rigid shapes, will make small openings like cracks and crevices where waste and detritus will easily fall in to and will be out of your reach when you go to clean the bottom of the tank, which you will inevitably have to do when waste builds up. Your clean up crew will take care of most of the waste and detritus, but won't be able to get it all and any of it that has fallen through those tiny openings that the crushed coral so graciously provide, will cause excess nitrates in your tank, which will lead to bad water quality. What you would want is a sandbed since waste and detritus will collect at the surface instead of falling through tiny openings and will be easier for you and your clean up crew to get to.
In my opinion, i say ditch the crushed coral or the seashells, and just put a nice clean sandbed made from DRY aragonite. In a small tank, you will need all the help you can get to keep your water quality clean, and crushed coral or seashells certainly won't help you at all.