Frogspawn wont "stay small" per say. It just wont grow as fast as an anemone or somthing like that. However the clowns may not nest in it anyway, ive only seen it once, and that frogspawn was the size of a melon. But in general black and whites are some of the least pickey clowns, which is what those were, so if you are planning on trying it, I would go with those.