So if I put a betta in a 5 gallon could I have anything else in there with them??
Well, you could always look at getting a Nerite snail, or some sort of shrimp (mixed reviews on shrimp).
Male betta fish are really territorial, their tank is really THEIR tank, and anything you put in there with him is in reality trespassing. It would only be a matter of time before they turn on the other fish.
Some others may nip at my his delicate long fins too. I really wouldn't recommend stocking anything but a betta and some snails in a 5g tank. The ecosystem is too easily disturbed, and betta aren't very happy in any community setting.
A couple of small snails. IMO, that's it. I had a betta nearly die after swallowing a ghost shrimp whole, and will never recommend mixing those two species. Any other type of shrimp will be a very expensive snack for your betta.
How about neon tetras???
Neons are too active and require too large a school for a 5g, even as a species tank.
I've got a mystery snail in with my betta. He stayed really close to him for the first few days but there were no attacks. Now Cthulu (the betta) doesn't even pay attention to the snail unless he's got food.
In a five gallon, I wouldn't put anything in but snails. Bettas are territorial, and they can live in community tanks, but you have to have the right betta and perfect stocking and ensure that the betta can have his space if he needs it.
Tetras are definitely a no-go. They cannot thrive in a 5 gallon, and there are some reports of them nipping a betta's fins.
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