Ms.Bubbles said:
To me, 5.5 gallons isn't really big enough for a betta--add several snails and an otto and the tank is overstocked IMO. You may enjoy a more crowded tank geekrockgirl. I know my betta needs nothing less than 10 gallons or he becomes very unhappy and hyperactive (and he would never tolerate a tankmate, not to mention 3!). Also, many people feel that ottos are happier in groups, but a group would not be possible in a 5.5g tank.
Wow - I don't know where you're getting your bettas from. But I currently own seven bettas, only one of which lives in a tank larger than 5.5g and she's in a well stocked community 20g in which she lives a very happy existence for several years now.
My others are all in large bowls, or in a 5.5g tank in which live two corys and a bamboo shrimp. I would hardly call it overcrowded, nor does my betta show any signs of being pissed off that he is sharing his space.
The bettas in the bowls have lived there for quite a long enough time for me to have noticed if they're not showing their best colors; but these fish are vibrant - building bubble nests and eating profusely. They're the picture of perfect health and have been for longer than I care to count.
I don't mean to flame you, but sometimes I read certain posts and I just simply cannot understand where people come up with their notions...especially the thing about overstocking. Snails don't even count very much towards the bioload of a tank; nor are they looked upon by the fish as anything more than a moving rock or a piece of food. Basically there would be a little more than two small fish in that 5.5g - hardly overstocked...I could even call it slightly understocked compared to most tanks. And I'm a fan of sparse populations. Not to mention that the betta and the oto are two fish that have very little space requirements after all. Neither are hardcore swimmers or marathon runners. They generally like to just float (betta) or attach themselves and meditate (oto.)
I've never noticed otos to need friends either. Most of the ones I have (and I've had them in all of my tanks) pretty much keep to themselves.
All bettas have their own personalities and being an owner of more bettas than I even know what to do with, I really do feel that generalizing their needs and behaviors is not the best way to tackle this given situation. If your betta needs a ten gallon to himself, that's fine - but I have heard of (and experienced) bettas who actually dislike being in anything larger than a bowl. It's all about the individual fish.
That being said, I will reiterate what geekrockgirl said - try out the oto and if mr. betta makes life for him difficult, find the oto a new home. But I have had bettas live with otos in both 2.5g, 5.5g, and 20g tanks. Not once was there anything close to an issue. There it stands.