Is it okay to put a fish with other fish after it's been alone for a while?

[Emily Kate F]

I have this Tiger Barb. He was wrongly accused of killing off all of the other fish in our last group of aquarium fish because he nibbled. He ended up being the last fish alive in that aquarium so everyone agreed on killing him so that we could get another group. I didn't like the idea of murdering a little Tiger Barb so I put him in a fish bowl in my room. My mom told me not to. She said he'd probably die and I'd be sad but that was four months ago and he's still alive and well. I've created a bond with my little fish so I did research on Tiger Barbs and found out that they like to swim in groups, like space, and like hiding places. I felt terrible because he hadn't gotten any of these in an empty fish bowl so I've been thinking about getting a new fish tank with a few more Tiger Barbs and hiding places and stuff, but I'm afraid that it might overwhelm him or something. Would it overwhelm him? Would it be better to give him a proper environment or just let him be?