So it's not cycled? What does not setup long enough mean? What does stable mean? We use numbers in ppm measurements for ammonia, nitrite, and nitrate to determine stability. How long has this tank been cycled? How long has he been in the aquarium?
All the symptoms described so far also indicates a stressed out fish still getting used to its environment, unless you've taken a fecal sample and put it under a microscope. An 8" fish can last a few weeks of not eating. I've easily had a 6" fish not eat for 1 month, and not have a sunken belly. She didn't have parasites.
I put water into a brand new tank then put water clarifier into it as I do with all of my tanks, I let the tank cycle for a day or two then I introduce the fish. What I mean by it hasn’t been setup long enough for nitrogen compounds to build up enough to do any type of harm to the fish, anyways what I’m saying is I don’t keep up with ph levels, I do weekly to bi-weekly water changes on all of my tanks and I doubt the green terror got anything from my water,he got the parasite when I got him I’m 99% sure he was a trade in where his original owner knew he was sick and just got rid of him for store credit.