SquirrelOsO, I don't think anyone meant any offense, and I'm definately sure I didn't. A lot of folks don't read into old threads or follow them closely, so starting a new thread with you questions will get more people to read them and respond specifically to what you asked. You can copy and paste what you've already typed right on to a new thread with a new title and folks will be more apt to read it. As far as your questions that I can help with:
Hith is far easier to prevent than a lot of people seem to think. keep your nitrates low, make sure your fish have a healthy diet, and keep them in a big enough tank to house them comfortably and handle the bio-load they create.
I'm a firm believer that there is nothing to fear if you understand the typical causes and contributors to this disease. I have never ever had a case of HITH start in a fish I raised myself. I have adopted several fish with HITH back in the old Days, but never had it start on my own fish.
once a month 50% water changes would seem very inadequate to me, I change 60% a week and feed far less than most folks do. My nitrates still hover in the 10-20 range and I have live plants in my tank. I do have what I consider to be a crowded tank (see signature on 115g) , but by some folks standards it is virtually empty.
Nutrituon is extemely important. I avoid goldfish as a food source entirely, I feed a good quality cichlid pellet as a staple and supplement with live snails, shrimp, and guppies. I raise my own guppies and feed them sparingly so the fish do not become finicky about the pellets. I also feed a variety of frozen foods but not in any routine manner. Goldfish quite simply are low nutrition, high fat, and most Oscars you've ever seen with HITH were fed goldies at some point. Oscars do not need live food as a source of nutrition. they like live food, and I believe it is good for their personalities, and well being, but small guppies and snails will allow them to hunt without all of the waste and pollution created by larger feeders.
I've not done any research or heard anything on Flagyl. I gave up adopting sich fish, so I haven't had to deal with Hith since I re-entered the hobby. I do occasionally use liquid vitamins, but there is some controversy to how helpful they are really. If I had a fish With HITH I would definately supplement vitamins daily, but healthy fish on a good diet probably really don't need them IMO.
dave