After reading all the post and how you are saying your puffer is eating good, I have a feeling you just have a lazy puffer. Mine is about 6 to 7 inch's long now, she was about 1 1/2 when I got her. She has always been very active, swimming all over all the time. They like tank mates and other fish to swim with. She was in a 150g that was old and sprang a leak, she is now going into a 210g this afternoon, can't wait to see her in it. She loves her krill, but also eats the frozen cube food that I feed. I stop and get her live clams for treats, which she loves. Good luck they are awesome fish, mine is like a dog, wags her tail at me and when she wants attention she spits water at me.