I would suggest not putting the Beta in the 10 gallon, I tried putting one in a 10 gallon with about 4 Black Skirt Tetras and he would harass then to no end, so I took him out and put him in a bowl then I got a 25 gallon tank and tried it, but he chased after everybody in that one too. Then I upgraded further and got a 55 gallon tank and tried it (figured the more room, he might not be so aggresive), but nope he is very aggresive. So now he resides in the 10 gallon tank by himself. And he seems to love it better than a bowl, he has lots of room, filter and heat what more could he ask for. But if you want to put him in, I would suggest you keep the bowl ready and put him in and watch him, if he starts harassing the other fish take him out and put him back in the 2.5 gallon.