Avoid goldfish period, they contain thiaminase, an enzyme that breaks down thiamin, a B vitamin. Prolonged use will shorten your fish's life. If you feel you have to use feeders, stick to tropicals and raise them yourself. One reason they're so poor in nutrition is that commercial feeders are fed the cheapest food available.
Get your initial stock, treat them for parasites, internal and external, then feed them a high quality food. Watch and raise them like your regular fishies and there go three concerns; nutrition, parasites and disease.
Worms and gut loaded crickets are still more nutritious, mine only get feeders when the guppy/quarantine/hospital tank threatens to overpopulate.