I plan to keep my african dwarf frogs with a Betta when i finally get the new tank-it will be a 64L planted tank so plenty big enough. From my researching some male Bettas just do not get on with any tankmates, but most seem to be ok with peaceful non colourful tankmates. The ones i have seen mentioned time after time as Betta tank mates are ADFs and corys, but as lilfishie says it really all depends on the size of tank you have.