A good beefheart mix will get fish to grow quite a bit faster, and depending on the fish could be fed once every other week to daily. If the beefheart you are buying frozen has any white streaks in it don't waste your money, they didn't bother to trim it properly. Trimming beefheart before grinding is tedious, but makes for a high quality food.
A few other aquarists & I get together a couple times a year for a little beefheart party. After trimming out 20 or 30 pounds of heart we double grind it, and add flake food, spinach, multivitamins, garlic, some seafood, and whatever else we think may be good.
Granted, beefheart isn't something that fish are going to eat in the wild, but tropical fish aren't going to eat things like cod or salmon found in a quality flake food either.