I have a ten gallon fish tank, a 55 gallon fish tank, and 3 betta bowls. We also have a 40 gallon long tank wit our hermit crabs in it. Our cats show zero interest in any of the tanks, for the most part. When we first got the fish tanks, they were interested, but after they realized they couldn't get the fish, they lost interest.Gaylord does like to frink out of the betta bowls, but he never bothers the fish...and the fish have fun with him...they always flare up at him.
We have only had 3 bad incidents with the tanks VS the cats:
1- One time, Gaylord and Ivan were chasing each other around, and they jumped up on the bathroom counter, where I had one of the betta bowls at the time. The crashed into it and it fell and broke. Luckily, we were able to rescue the fish.
2- Ivan was once climbing around, trying to lay on top of the ten gallon tank to take a nap. Well, he has gained a bit of weight, and "PLOP" he broke the glass lid right in half and fell halfway into the tank!!!
No fish were hurt, and we repaired the lid.
3- (This one was OUR fault, not the cats)--about 2 months ago, we accidentally left a container of sea salt sitting on top of our 55 gallon tank, and left the lid ajar....we woke up the next morning to see that one of the cats had knocked the salt into the tank...killing all our fish.
Basically, just use common sense, and be observant....I say go for it.