Another important question - What is your choice of substrate?
Deep Sand Bed
Shallow Sand Bed
Bare Bottom
Crushed coral
Sugar Sand
Your choice of substrate will have an impact on the animals you decide to keep as many animals need to be able to burrow.
Have you already purchased live rock? Do you plan on making your own live rock, aka aragocrete, and seeding it? Many people swear by the method of cooking their rock when setting up a new tank so this is something to think about as well.
The more time you spend planning now, the more you will enjoy your tank later and the less hair you will pull out trying to solve problems.
