Fish Help

My friend has gouramis and a tinfoil barb in like a 2 gallon tank.

The fish seemed alive and healthy (not happy) last time I went and saw his tank. Obviously it's kind of ridiculous for the tinfoil barb but now he's saying the barb killed all of his fish.

I have a 20 gallon tank with neon tetras and corydoras so can I take the tinfoil?

Basically, can I keep tinfoil barbs with neon tetras in a 20 gallon tank (even though I know 20 gallons is too small but it's better than a 2 gallon)?

Thank you for the advice.