If you have any questions on coral or fish or whatever you can ask me anytime. I'm not an expert or anything but I do have a lot of experience in salt and fresh water fish and corals. I have had all sorts of stuff in glass cages pretty much since I was born. I have raised clowns, I have propagated corals and have sold both. PM me, Tag me whatever, I have made all the mistakes, and have had a lot of successes also. I check the site regularly as of now and your thread is in my watched list. I hope this doesn't come off as conceited, that is not what I'm try to say. I just want you to know you can ask me just about anything, if I have had experience in the matter ill give you my thoughts.
As for clowns that tank is going to be theirs, anything you put in after will most likely be harassed to the point it hides or dies or kills one or both clowns. Just my experience in a smaller tank, they need about 3 sq feet especially if mated and breeding (breeding probably more).