I believe in feeding sparingly, except for fry of course. Mature fish that are healthy only need one small feeding each day, and missing a day or two (like water changing day) each week won't hurt. Some of our members even feed alternate days only. Healthy fish can easily go a week without food, which tells you how little they actually need. And most of the good fish foods are highly nutritious now. Fish will (or should appear to) be hungry always. In nature they are always looking for food because it is scarce. So overfeeding can be easy to do if we are not careful. A hungry fish is a healthy fish.
As for foods, reputable brands are Omega One, New Life spectrum [hope I got the name correct this time
] and Hikari. I use the first and last of these; NLS isn't available locally yet. For upper fish, flake and pellet foods; substrate fish should be fed sinking foods specifically made for them. Don't count on some flakes getting down there. Unless you are feeding too much at one time, none will.
Variety is the spice of life for fish, plus it ensure good nutritional coverage. Several types of flake/pellet and several types of sinking foods. At present, with my 7 tanks, I alternate daily between 3 flake/1 pellet for upper fish and 4 sinking for substrate. One of each should be veggie-based; I am using Omega One's Kelp flake and sinking disks. The others are Omega One Colour flake and basic flake and Hikari's micro pellets. For sining foods, the Omega One disk plus Nutrafin's tablet [for some reason the fish are crazy for this], Hikari's basic sinking disks and Omega One's shrimp pellets.
And, welcome to Tropical Fish Keeping forum.