gars will instinctively hunt at night. they will of course feed during the day too, but it's within their nature to prey at night. in fact, most fish species feed primarily during crepuscular periods, which are the periods of lower light during the night/day cycle (dusk/dawn).
as gars get more and more used to their captive environments, they will get used to feeding during the day. of course, this is most noticeable with non-live food (the food most recommended for gars and other predatory fishes). the occasional live treat is ok, but it's much healthier to give them a diet of frozen shrimp, fish, krill, and various pellets.--
--solomon