While as of right now my CT male Phish (pictured in my avatar) is in a filtered, heated 2.5g tank, I have plans to upgrade to a 20g tank once my fiance and I move in October. I have the tank already, courtesy of a regular customer at work who had upgraded his own tank and wanted to give the old tank (along with the filter, heater, hood, and the fluorescent bulb still inside) to someone who knew how to care for fish as opposed to donating it to Goodwill.
Anyway, I had been wondering what sort of bottom feeders would be compatible (assuming compatible personalities of course). I had been looking at cory cats, since they seem to stay fairly small and so I could fit a few of them. I like loaches too (particularly dojos), but would those get too big? I have also considered ghost shrimp.
I'm also open to other suggestions for tankmates, including any community fish if there are any that won't provoke a betta (I seem to get different answers depending on who I ask at pet stores). If it helps, I also intend to plant the tank.