Bresn, I think what you said is exactly it - 2.5 gallons is fine. Much better than the tiny bowls, gives them some room to swim around. But, it's still only 2.5 gallons. It's like saying a 15 sq. ft backyard is fine for a dog to run around in. Yes, it's fine. Would the dog prefer a couple acres to run around in? Absolutely. It depends on what your ideal is, and how active the fish is. I have 2 female bettas in a divided 5 gallon, and I think it's fine. I also "rescued" them from the tiny bowls my office had them in before I started working there, so it was a big upgrade for them. Right now I have a betta in a 10 gallon community tank, and she swims the full length of it very frequently. I'd feel terrible about putting her in a smaller tank now.