Bosemani Rainbows

No, sorry, they would not. A 20g is too small as it is, add to that the fact that yours is a high and it's just not a feasible situation. Boesmani Rainbowfish are active swimmers that can reach 5" (6" for a big old male). Plus, they are a schooling fish so they should be kept in groups.

Actually, a 20g is too small for an adult angelfish too. Mine is about busting out of his 29g tank. Of course, that could be a good reason for upgrading