Pichi, my halfmoon was in my 40g breeder that I had divided and had about 8 gallons to himself.
He liked it well enough for a week but I came him one day and he had 2 MASSIVE chomps out of his tail x.x
So I shifted everyone around and he ended up in my 5 gallon by himself. I figured he started biting from being housed with other male bettas, even if it was divided. He stopped biting but was a bit listless. I assumed it was from not having a heater in the tank (Its on my buy list)
THEN situations changed and I had to divide my 5 gallon. Decided to take a chance and throw in my other tailbiter, Chai, on the other side.
Pichi now scoots along the tank and never stops, he's brightened up and his fins are just about grown back. Hes so enthusiastic, I imagine him screaming like a toddler every time he swims across his meager 2.5 gallons LOL