On a daily basis, any one of about 5-7 types of generic flakes (cichlid, colour, whatever other free sample I've gotten recently), small sinking pellets by Tetra, TetraPrima (because I got it for free), floating Hikari pellets or unbranded floating pellets: twice per day, as much as they can eat in 30 seconds. Also, 1/2 Hikari algae wafer per adult pleco: once per day.
1-3 times per week 1/2-1 large cube of live food (bloodworm, white mosquito larvae, black mosquito larvae, cichlid mix (shrimp, etc), beefheart, artemia, cyclops, some other stuff) instead of dry food.
1 day per week without any food.
Occasional veggies and live white mosquito larvae, + and household bugs which get themselves drowned.
The diets do vary depending on which species are in the tank. I find that the fish benefit from a variety of foods, probably because no single food can provide a good balance of everything the fish need.
Fry and young fish are sometimes "power fed", by which I mean that they can get fed protein rich foods 6-10+ times per day, but the amounts of food have to be minute (sort of everything gone in 5-10 seconds type of small) and the fish then produce a lot of waste, so daily water changes are needed just to remove the waste and keep nitrates low. I would never give a diet like that to an adult fish because it is very likely to harm them. From my own experiments, fry on this diet will grow up to twice as fast as fry on a normal adult diet.