are you familiar with the cycle that your fish tank has to go through? if so, you have to cycle your tank, and you could probably get a clown and a small goby, or other small fish after the cycle. clowns are good because they are pretty hardy, and both are not too big or messy. most people will tell you no more, but i would say that after you got pretty experienced you could put antoher small fish in there, depending on your filtering and live rock. but for now you have to start your cycle, you can do this with either a piece of raw shrimp, or a damsel. put it in there, test your water, wait till ammonia goes up, then to 0 and nitrites go up then to 0. then you can add your clown, after you take out the damsel. good luck, and take it slow.