I have a pair of spawning tomato clowns. Their larva always wind up in the sump and I bet if I grew rotifers and brine shrimp I could get them to grow out. Any larva that remain in the top tank are chow for the other fish though.
I'd say zero too, but there are always exceptions. I had a customer that had a pair of gobies (sorry forget the species) that spawned and he found babies in his overflow box. Ditto my former employer had a pair of Banggais in his 600 reef....they spawned regularly and occasionally we'd find a baby in the overflow box, who had beaten the odds and avoided ALL the fish and corals and inverts....
This morning I've got baby seahorses in my overflow box. I've had miserable results trying to raise them in a nursery tank....I am almost considering leaving them put.
