I have 2 fig-8 puffers in a 160L tank, SG 1.005 - all parameters good. I have had them for 5-6 years.
Recently I moved house and re-setup the tank. I also added 3 mollies. The puffer's behaviour changed dramatically - only eating when not being watched, no longer playing "chase the finger" and darting away rapidly at the slightest movement towards the tank. This went on for a month. I checked the parameters, did water changes and even removed the mollies. The puffers still had beige bellies and were timid, sometimes resting on the bottom and doing nothing.
I, by chance, think I discovered and solved the problem. When I set up the tank my wife said she actually preferred it with no backing on the back. Instead just the plain white wall behind. I have just put the old plain dark blue background on the back and noticed a 100% improvement in a matter of minutes!
It was as if I waved a magic wand. My puffers are back to normal.
Hope that helps somebody who may be experiencing similar.
