I have a foot long + in a 125g. Loves to stay under driftwood....had to find a piece big enough. I keep him well fed so he doesn't bother the other tank mates (anywhere from 1 1/2 in to 4 in). I did have him in a tank with my large pacus, which I had for over 7yrs. I thought the pacus were going to eat him alive!! They just kept picking and biting at his fins and whiskers for months. Poor thing....well, you see who I kept.....my tame, handfed kitty fish,...and my old 7 1/2 yo oscar, who doesn't bother anyone.