What size Clownfish can I add?

I don't know if an ocellaris clownfish are capable of each growing to different lengths, but my lfs sells mediums. Although some are smaller than others and vice versa, is it ok to add one that's almost full size, as my first fish in my 20 gallon nano. Or does it not matter?

 

good question, you should be able to house the fish in your tank whether it is a baby or an adult. the occelaris clown would be a good choice. If it is larger it may be a little aggressive to other fish you add after it. That clown will fit as an adult in your 20g.

 

All OC clowns grow to roughly the same size. So, it really dosn't matter, unless, as nc208082 mentioned, if you have other peaceful, or aggressive fish. If you have other peaceful fish, the younger (smaller) clowns, will tend to be less aggressive, which will give the fish more time to work out their territories, before the clown gets older and becomes more aggressive. On the other hand, if you have other aggressive fish, a bigger clown will be better able to fend for itself.