I have never seen the dark spot tummy thing unti recently, when I knocked out one of my fig8's to trim its teeth. I was worried seing the dark colors on the belly, but they did go away in minutes of him swimming back around.
that's good to know... I haven't had puffers for quite some time now and when I was, I was led to believe that they did indeed release toxins. Goes to show you just how much things change and the learning can be far more advanced in just a number of years. Thanks for the heads up PF!