How to decrease mortality rates of clownfish fry?

At school there are breeding pairs of percula and maroon clownfish. Both pairs have produced eggs, and the eggs have hatched. The fry keep dying, and only 3 fry from each batch survived. They are fed on freeze-dried cyclo-peeze, and grown in a large system, exactly like the kind at pet stores only maintained more frequently. What triggers spawning and how can the mortality rate be lowered?