well, aside from the thiaminase, goldfish are simply not very nutritious to begin with. You may notice some slight oddities to the way the snake moves, which may or may not worsen as it ages. The life span of this snake COULD be permanently shortened. It may not. No way to really tell. The snake may be permanently stunted. a lot of people don't realize just how BIG ribbon snakes actually get!! I would not worry about that, just focus on making your snake as happy and healthy as possible in his new home