We have had our Betta for over a year now with the 5 cats. They pretty much ignore him now for the most part. Every now and then they will watch him for a while and Trouble will dip his paw in the back of the tank near where the filter is. We have a 2.5 gallon tank with a light and filter for him. I would suggest getting something heavy enough that the cats couldn't push it off of whatever furniture it is sitting on. Ours is named Stick. It was when Brian was working at the bank and they all had bettas. The customers would ask what his fishes name was...he would reply "Stick". Some would get it right away and some would start to walk off and then get it....Fish...Stick.