I have a 10 gallon and a 20 gallon tank. I have 3 fish causing some issues: a betta, a fancy male guppy, and a pea puffer. The pea puffer presently lives in the 20 gallon and the other two share the 10. Now, the guppy has outlived the other guppies I bought with him. He's fairly old, but that doesn't stop him from being a massive jerk. The reason why he's living in the 10 was not only for his own safety (I think the pea puffer was nipping him) but because he was harassing other fish. However, I now am keeping my betta in the 10 gallon (gave the betta tank to a friend's sick fish that seriously needed an upgrade) and the guppy seems to have bitten his tail. I'm considering moving the betta and the guppy into the 20 gallon and moving the puffer into the 10, but I'm not sure if the added space would help that stupid guppy's temper, nor am I sure if my betta will be okay with the added space and other tank mates (a small school of neon and glowlight tetras). Any advice/suggestions are welcome.