not a whole lot of time to get into great detail right now, but here's a couple bullet points:
- if all your gars are roughly the same size as the one you have pictured, you are fine with feeding them the way you are...especially with your described schedule.
often in raising YOY (young of the year) gar, i will start them off with feeder minnows and just dump a bunch into the tank and let them pick them off on their own until they are gone.
-YOY fish need to eat frequently and a decent amount, and their growth rate and behavior reflects this, even in captivity. you won't really deal with any detriment to "overfeeding" the gars at this stage. once they get to 10" or so i would scale back and try switching them to non-live such as frozen, etc (you can better control feeding that way too).
-even though all these gars are from the same cohort, genetics and behavior will cause differences in size. one will likely dominate the other, but as long as they are all growing and one doesn't get so big it can eat the others you should be ok.
-in dumping in a lot of minnows, just be sure you aren't getting a mass die-off which can cause ammonia spikes and cause problems for the gars and the biofilter...as long as they are all being eaten you should be ok with this system for a couple months.
keep us posted and let us know if you have further questions--
--solomon
PS-- in feeding like this, be sure to keep up with water changes! 50% each week is a good start--