My mom recently got a new fish from Petco. He seems youngish and pretty interactive, and one of the more healthy ones there.
But when we brought him home he wouldn't eat. We figured it was just because it was new environment so we gave it a few days, and tried several different food kinds and brands.
It's been two weeks now and he still doesn't seem to eat. He'll see the food and either just ignore it, or go to eat it and spit it back out. It's like this with all the food we've tried, which has been about 5 different brands/kinds (flakes, pellets, brine shrimp...)
But he's active! He interacts with you and his environment, swims around chipperly, and doesn't spend any certain amount of time on the bottom or top of his tank (3ish gallons). His fins are fine, and doesn't look like he has any fungus. He just seems to be acting like a healthy fish, just not eating.
What should we do? Should we just look into a better quality food?

That's him from the second day we had him, if that helps at all.