i had this random thought today. bettas dont like other colorful fish, they (supposedly) will not attack larger fish. yes i know every fish is different and it could end in disaster but i was thinking ...
Ropefish? like maybe 1 they are large, not colorful and active. I've had them before and iirc they eat bloodshrimp/ beefheart. I doubt my betta would complain about that.
this is a ropefish if you have never seen one
EDIT: google pic may have awnsered my question...that looks like betta fins in the right hand side of the pic.
still though, im curious if anyone has ever tried this as a tank mate.