Just a reminder: you should NOT feed goldfish or rosy-red minnows to saltwater fish.
Although this used to be considered safe, on the assumption freshwater parasites wouldn't be transmitted to saltwater fish, it is now understood to be less than ideal. Goldfish and minnows are nutritionally deficient because they contain a different balance of substances to saltwater fish, so any predatory marine fish given them is effectively being starved over time, even though it seems to be eating fine. Bob Fenner has done autopsies on lionfish that were fed goldfish, and they invariably had liver degeneration and gut abnormalities. In other words, using goldfish to feed marine fish isn't just inconvenient, it's harmful to the predatory fish.*
Guppies and mollies are far safer (having much less fat than minnows and goldfish) and can be easily bred at home, so responsible aquarists can make sure they're disease free before using them. You can also wean most predators onto alternative foods without much trouble, and doing so allows you to use a wider variety of foods. The more varied the diet, the healthier the fish (just as with humans).
According to Bob Fenner and others, feeding live feeder fish also makes lionfish more aggressive, something you don't want.
Cheers, Neale
*See: The Conscientious Marine Aquarist page 207.