I have a Blue Hippo in a 75 gallon. I got him from someone that had him for 12 years in their 75 gallon they were tearing down. This was five years ago so he is now 17+ years old. He is small at only 6 inches but he eats and seems happy but thats tough to tell since I'm not a fish shrink. Would I put another one in my 75 probably not but I was trying to prevent this guy from just getting rid of the fish. But I have to say 17 years is a long time for a fish to live that shouldn't be in a tank that size so I have to question that a little. My guess is there are not a lot of 17 year old fish out there.