If you are doing a shark tank youd want to have a little rock but not a whole lot. you dont want to take away the sharks swimming room. because you dont have LR youll need a Wet/Dry. the best in the biz is proclear and this site sells them. you will need a skimmer as well but you need to nail down a size first.
to explain a wet dry is a sump with bio balls for bacteria to grow on and mast of the time as stated above it grows on our LR but with you not having much youll need it.
A sump is any body of water outside of your tank that holds water, has an open top (no lid) and is conected to your main tank. so a wet/dry is a type of sump. You may be thinking of a refugium or fuge for short. most of us use this type of sump becaus we dont need a wet/dry. pluss a W/D's bio balls are bad about letting detris and other gunk get traped in between them. the detris then rots and creates a spike in your ammn. and may kill/hurt your fish. so its important to rence them off in old tank water every now and then to keep them clean.