I have a 5 gallon and in it I have 1 male betta and 1 cory, 1 snail and 2 otos (I originally had 2 cories, but one passed away before I could buy another and the otos I just put in because the tank is filthy. I transferred them from my other tank for the time being since the other tank is spotless where algae is concerned.) I don't add salt to the tank. The only time I would add salt is when the betta is in the 1 gal hospital tank... knock on wood this has not occurred and he's been healthy. So, it is an option to have otos, cories and snail in the tank, but when a fish gets ill you want to separate into a different tank to prevent the spread of disease. I don't know if you have a walmart near you, but they have 1 gal tanks for 10 bucks (max) that you could use as a hospital tank...