I had a bowl with fish, and with long lasting efforts I made it quite successful. It is not recommended, but it can be done.
Why not recommended? Simply because the environment is too small, and the fish do not have enough space to move. It is like a jail for them.
As bottom feeders, I had a small school of albino corydoras. They are social, so you should have several of them, I remember a rule of about minimum of six - otherwise they get lonely. They do their job all the time, being busy scavenging. They never attacked anyone, and they are quite robustly build (even though small) so there are small chances to be attacked by other fish. I had them for the entire life of the bowl - about 6 years - and the same school from the beginning was there all the time, no replacements made.
As bottom dwellers I also had ancistrus - I liked them for their shape and colors.
I had tetras, betta, occasionally guppy, others. I never noticed any fights and any damaged fish.