I was wondering if anyone knows of why my Mbu puffer has spent his entire life in basically one spot of the tank. He can swim, but chooses not to all the time. He eats and is healthy but truly never swims around the tank. Hoping that someone can help me out with why my Mbu has never really been a swimmer. He is 6 inches, I have had him since 2-3 inches. Please help and give me advice. Thanks