Food!!!
Probably the most important thing for successful breeding, next to water quality, is the proper diet. Both for your broodstock and your juvenile fish.
While many types of fish will spawn in an average reef tank, quite often the eggs won't be viable or of low quality due to deficiencies in the parental diet. Spawning fish need to feed often and have a well balanced diet, just like us.
I feed my broodstock pairs four times per day, every four hours. Feeding like this would rapidly cause issues in a reef tank, that is why most breeders choose to isolate their breeding pairs.
I'm not going to get into the scientific dietary details but you can find my feeding recipes below: