I feed frozen food one time, then next time flakes. 25% weekly water changes.
If you add flake food you will see them go crazy at first, then add a small amount more after they finish that, they will slow down. Keep adding small amounts for just a couple minutes. That is all they need. I use a feeding ring to keep the food all in one place. Easier to make sure they are eating what you are putting in. They are cheap and suction to the side of the tank.
Frozen food is tougher. I usually thaw it in tank water first, then strain the water out. They have itty bitty strainers that I found about 3-4 inches across. Great for this. Then I put the strainer in the tank and swish it around. Hard to control what comes out. It all floats around. Can't be helped. I usually come back 10 minutes later and can't find a spot of any food left. They find it. I find it fun to see their fat little bellies after having frozen stuff.
The more food you put in, the more comes out, the more ends up as nitrates in the end. I feed light to keep the trates down.