I feed new life spectrum small fish formula and just feed mine a small pinch at a time (maybe 10 pellets). I let them eat that and then do another small pinch, as many pinches as they can eat in around 1 minute. Which is usually 2 pinches... So I'd say I tend to give them 20 or so small pellets twice a day (for 6 fish).
As others suggested, just a pinch - try different varieties of flake, NLS food. I use a fish-only pepper grinder to grind down the food ( used it when I have fry as well ) so if you decide to go that route, 2 grinds with a pepper grinder is sufficient for 5 fish - they are pigs and will eat and eat so even though they seem hungry, don't give in
You are right to consider feeding seriously. This is the main source of pollution in the aquarium leading to poor water quality, fish stress and disease.
In addition to the amount fed, a good quality balanced food that is digested properly and absorbed by the fish is equally important. I expect that all well known brands of tropical flake will satisfy this requirement.
Fish have less than 10% of the energy requirements of mammals so you may be surprised how little food they need.
I feed 2 flakes per Danio per day.
This picture is of my fry tank.
The 2009 scientific study of the energy requirements of tropical fish found that Leopard Danios (a variety of Brachydanio rerio) need less than 7.2 mg of flake per day per fish in order to maintain bodyweight. This is equivalent to less than 2.4% of their bodyweight or less than 1.2 of the flakes (brand not revealed, but a balanced diet) used in the study.