How many Clowns

What kind of clowns? Some, like maroons, tend to be very territorial and not friendly to more than just their mate. Others, like perculas, will live in a harem setup--the largest fish will become female, with the next largest her mate. The other, smaller fish will stay small and male until something happens to the pair. Some fighting initially is normal, but given enough space, you could have 5-6 easily. Adding them all at the same time will work better, since any later additions will be unable to claim territory and constantly harrassed.

I wouldn't try mixing types, though--very nasty fights. I had a pair of perculas, added a larger maroon a few months later. The perculas beat the crap out of that maroon overnight--it was so beat up it would sink to the bottom, and one of the percs would grab a fin and haul it to the overflow, where it would be swept out of the tank. I was horrified--pulled the maroon out, and saw it happen again. The maroon was removed from the tank, but died from it's injuries.
 
Are you sure you want only clown fish in your tank! You could have 1 pair and some other fish. But you could have like 10+ fish in your tank but I think that the clowns are to terretorial towards other paris so check with your LFS. But I think that you should get different kinds of fish.
 
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