I've had a Betta in with four Danios but they are very individualistic fish! Some just have more relaxed temperments and others more aggressive. Aggression is also a learned behaviour for them. Each time they use aggression successfully it reinforces them.
Like people said. Don't put them with nippy or aggressive fish. Don't put them with anything they may view as lunch (small shrimp, snails, very small fish) that you don't want eaten or wouldn't be good for them to eat. Don't put them with anything they might mistake for another Betta. Fish that are peaceful and calm but can outswim them are the best bet. If he reacts aggressively be prepared to move him. Bettas prefer warmer temps than some other fish but that's individual too. Mine is happy and very active at 74. You will have to take care to make sure the Betta gets it's food though. Faster fish will steal the food right out of it's mouth.
You can put plants in with Bettas as long as the Betta has lots of access to the surface for breathing. Unless there is something I don't know about lucky bamboo you could put some in, just not in one of those narrow neck vases. You'd have to hang it on the edge of the bowl somehow or let it lie diagonally but it grows directly in water and doesn't need much light.
Bubble eyed goldfish are not strong swimmers and can't defend themselves well. They will be out competed for food by most fish. They could be OK with peaceful bottom dwellers , snails etc. You would have to keep the tank very clean depending on how tolerant the tankmates were. Snails wouldn't mind the mess though.
Eunen_de
i have my betta in a 15 gallon with platies and 2 cory. THey keep each other amused. my playty will swim right up next to the beta and he dosn't care, they just all swim around, not caring about each other. there are lots of fake plants for them to hide in and a sewage pipe ornament. i also used to have 1 male in with 2 females in a 5 gallon. the male was supposed to be a female.they got along fine aswell. and i friend of mine has 3 females in a 5 gallon, an dtheir all fine aswell. i dunno maybe the local fish store gets calm fish......
