What is the height of a Clown Fish?

There are about 50 different species of clown fish, not just one. The one you are probably referring to is the False Percula, Amphiprion Ocellaris. That was the fish pictured in Finding Nemo. That fish is one of the easier fish to raise in a saltwater aquarium; they only reach 2-3 inches in aquariums, (5-8 centimeters).

Among the other species, the largest of them is the Maroon Clownfish - Premnas biaculeatus. The female of this species can get about 6 inches long. All other species are generally between 1 and 5 inches long at maturity.