I have heard, someone please correct me if I am wrong, that fish have a memory of about 3 seconds. I was told that the reason it's ok to keep them in a tank so small, compared to their size, is because by the time they do a lap around the tank they have forgotten what the rest of the tank looked like, therefor, they always have "variety" no matter how small the tank is. I am skeptical as to whether or not this is true, but fish are the creatures I know VERY little about so I guess I am asking you fish people if this was something said to me to help ease the pain of keeping fish in a tank too small for them.