i have two cats, and neither of them seem to pay much attention to my tank unless i am. My older cat, she is about three, absolutly hates when i pay attention to the tank and not her. she always rubs up against me when i am observing my fish, corals and inverts.
My younger cat, about two, likes to sleep on top of my canopy while i am at work. Lately everytime when i walk in the door i can hear her jumping down from on top of the tank.
When they were both younger, they seemed to like to try to catch fish from my freshwater tank, but since i had them declawed, they have left it alone. both like to jump up to try and catch all my fish, but that is about the extent of it nowadays.