Yes you can, for life, I would say you can keep up to 4 archer fish for life.
You can fit other fish, however a full grown archer get to be 8-10" in captivity, and can reach a full foot.
They eat pretty much anything.
Floating cichlid pellets/tropical flakes & pellets can be a main staple, supplemented with krill, blood worms, other shrimp or meaty foods.
Live foods can consist of guppies or small rosy reds, worms and especially crickets. They LOVE crickets.
However, I would limit the amount of live foods you give them (goldfish - ie guppies/rosy reds(toughies)).
Archers CAN sometimes be tough to get to feed, they should always accept crickets if nothing else, then you can work them onto pelleted/flake foods.