I would just suggest the bigger the tank, the better. Shiloh was always okay with my fish. She'd watch with interest but the only time she tried to get one was when a bala shark jumped OUT of a small hole in the cover of the tank where the filter was. Lucky and Chance were way too curious with them though and they somehow moved the tank (not by the cord) of one of my bettas. After that, I decided no more fish until all my fosters were adopted or until I move to a bigger place.