Thank you so much for your reply! Sorry for just now getting back to you, I've been swamped for two days.
We're now treating him with only Maracyn, and a second round of Jungle Fungus Clear.
When we do water changes, it is with medication-treated water from a pre-mixed gallon jug, as suggested! :]
I honestly don't know what he has. My instinct STILL says Saprolegnia, based on his first original growth - it was a large, pea-sized cotton out of his left gills. I can't VERIFY that it was injured tissue that it was growing on, but we assume yes, as he has some kind of fin rot that MAY be ammonia burn? We aren't sure, he has had perfect ammonia levels since he has moved to his hospital tank, but could have had a lot of damage done in the other tank with his roommates. But he ALSO has some crazy deterioration going on with his body, as I said, so we have been treating him with all regardless, as that was the best mix of medicine I could find based on four hours or so of research. If you have more suggestions for additional medicine, please let me know.
We did a 100% water change yesterday, and another 50% change today. He hasn't eaten since Saturday, so that's an awful sign. Really distraught. Do y'all know of any other masters of fish medication we could contact? [Not negating your suggestions at all! Just the more, the merrier at this point. We're devastated.]
Is DarkMoon17 still active? I'm DMing him/her, since a lot of what I'm going off of is based on his/her thread here:
Here are photos of Galileo now:
I know there are four prominent white spots on his lower body and tail. These are actually water bubbles, NOT growths on his body.
He's sickly, has a weird texture on his head, and is losing his fins and tail. He also just lies there, as you can see in this second photo.
That's what he used to look like. It makes me so sick to see how gorgeous he is. What have we done? ;_;
[If the first two photos don't work, they're also here: