I'm very pleased to report that Fantasia is settling very well into his new home. His new tankmate, Balthazaa, who is looking very healthy in quarantine, is very healthy also.
Fantasia's gills are growing back really well and there aren't any signs of fungus. He's not even going to the top as frequently as I expected him to have to.
Thanks for all your help!
Just a minor question, cos I dno't want to start a new thread: How long do I quarantine Balthazaa for? Both are looking very healthy and both tanks' water is healthy and the same, if that contributes...