Tomato clown can be aggressive toward other clownfish, esp after establishing territory and when larger in size. Pairing is best done when clowns are juveniles or bought already paired up. However I recently paired a large female ys marroon with a very small male. I let her get used to seeing him in a guppy breeder net hung on the side of the tank. Then let him into the tank after 1 week. They live happily now together in a bt anemone:happy: