Thank you for all the help. I heard red belly pacu can lose the red on their bellies. But also when I did a search on red belly pacu they more than not are always a lighter color than mine, and actually look like a red belly piranha. My pacu actually seems as dark as a black pacu. Why I wasn’t sure what I had. Also on my search it said red belly pacu get from 12”-24”. So to hear from you to say they can still get to 3 feet long was a little surprise. He is currently in a 125, he will be in a 220 in about 5months. I’m hoping that will be sufficient for him for two years till I can build a huge aquarium for him and his tank mates.