Actually, it's not good for fish either. It does stunt their growth to some extent, but once they have grown to be too big for the tank, they will start getting kinks in their backs a lot of the time, and generally be unhealthy and stressed. I had to talk a lot of people out of buying those little bowls for their goldfish when I worked at a pet store, and a lot of them didn't believe me when I told them ALL the goldfish we sold could hit 12 inches.
So far as snakes go...bull. Buy a baby retic, put it in a 10 gallon, and see what happens.![]()