you know, i've been thinking about starting a sponge tank. i think it would be a cool looking tank with all the different sponges out there. but as you said anomnies and clowns could be cool too. i was going to do a pony tank but posted a question about them, lets just say that unless you have a lot of free time ... they should not be kept. here is a link to my post for you to read ...

http://www.captivereefing.com/showthread.php?t=3359