this is actually a more complex question than it seems...depends on a lot of things...primarily the size/age of the gar, and secondarily, tankmates, tank size, water change schedule, etc.
for my sub-adult and adult gars, i feed them about 1-2x a week...generally a 2-day fast between feedings. feedings consists primarily of shrimp, with every other feeding being shrimp soaked in liquid vitamins.
for young of the year (YOY) and juvenile fishes, i feed them 1x each day, sometimes 1x every other day depending on the growth i am shooting for and their temperature/water change schedule.
what species and size fish are you asking about? we can tailor our answer to your fish specifically with more details--
--solomon
i think you nailed it on the head solomon. size of the fish and species is def. the key factor. the amount of food per feeding should also be taken into consideration.