The poop I see in his water dish from recently (could have been yesterday) is very very small, loose looking and green. I am very worried. His behavor seems mostly normal, except he won't eat. For a while he was not climbing up on his branches, but staying down at the bottom of his tank most of the time. That was unusual for him. Now he is back in his "favorite spot" again near the top, but still looks sick.
I very badly want to take him to a vet, but I don't think I can find one near me. I will check that link you posted.