That is contrary to everything that I have read and heard, but either way, you cannot keep clownfish with dwarf seahorses (they'll eat them and/or harrass & kill them and/or outcompete them for food; whichever happens first) and you cannot keep a large species of seahorse in a 10 gallon. So, if you're set on trying to keep a species of clownfish with seahorses, I suggest that you have a minimum of a 60 gallon tank, take measures to make sure that the seahorses get enough food, and do a lot of research on the problems that people have had trying to keep seahorses and clownfish together. I would also stop listening to whatever source told you that "black clown fish and sea horses get along pretty good".