Actually in nature what will happen is that once the clowns hatch, they will swim up to the surface following the moonlight and become part of the zooplankton mass (clownfish larvae have a pelagic stage). While there is a good chance they will become food, it is also a place where it is easy to find food. They will drift in this state for 10 to 14 days depending on temperature and nutritional factors then they will settle down to the reefs after undergoing metamorphosis (that is why some people call meta settlement). So in your aquarium, there is no way to provide a naturally ocurring pelagic zone. So as breeders we get the clowns through this pelagic stage by isolating them in a small aquarium with thousands of zooplankton that the fry can feed and grow on, of course, they have no predators, so the survival rate is many thousands percentage points higher than in nature. Once they go through meta, you could put them in a natural environment with anemones, of course if there are other fish, the little clowns could still be meals if they are mouthsized. After Meta, most clowns are still less than 1/4 inch, so almost anything would eat them. I don't know what percentage of clowns that hatch in the wild make it to adulthood, but it can't be high, think about the many opportunities for them to be predated upon. A pair of clowns need only have 2 survivors out of tens of thousands of eggs in order for their species to continue.