Depends on what fish and what size they are.
My 33 gal, I feed twice a day with flakes, just a pinch. I have 2 diff. brands so I alternate. Every other day they get frozen bloodworms or brine shrimp. Also add an algae tab every day. Skip one day a week.
For my 10 gal, same thing, but only less.
For my betta, bloodworms every 2nd day, or brine shrimp. And betta pellets, maybe 1 or 2 everyday.
I feed my newt in the 10 gal twice a week w/ bloodworms, ghost shrimp, tubifexworms, and sometimes guppy fry.