Just wanted to give a quick update: a week or so ago I bought Metro-Pro to treat the Hexamita. Dose every 24 hours for 10 days. It is working fantastically. He's been aggressively eating and even swimming up to get the food before it has a chance to get to the bottom. He's on his 5th day of treatment. After 5 more days, I'll observe him for a couple more days and if he's good to go, he gets to go back in the DT.
Humblefish, you have been incredibly helpful and patient. Thank you for answering my questions and for genuinely caring about my fish's health. High five!!