well, danios should be fine. a small school of them would be ok (5 or 6?) but the thing is, your betta might chase after them, but after a while, he may give up since he would eventually figure out that he cant get them. so yeah, they should be good. plants i use is java moss, and...ceratopteris thalictroides. i think soft leafy plants would be good since bettas tend to lean and rest on the plants, so the must be soft!