Okay, I guess it is time to add something from a medical standpoint.
Whether or not Melafix "works" on "curing" fish of disease depends on four factors:
1) What disease the fish has
2) How far progressed that disease is
3) What is Melafix's target system and its active ingrediant
4) The state of health of the fish before it got the disease
It's been a long while for me, because I have not used it in a while and do not have a bottle of it in front of me. But from memory, Melafix is a topical, used to treat skin (scale) infections that are fungal, bacterial, or "minor" trama related. In essense, it probably does help with fin repair and surface wounds the same way neosporian for us does. But neosporian won't cure gang-green, and Melafix sure ain't gonna cure a fish with rot half-way through a caudal peduncal.
Regardless of the smell (smell is no indication of potency or activity), if used in the right concentrations on the right regime, Melafix probably does do what it is intended to do. I know I have used it before with pretty decent results. Primarily I used it in a propholactic fashion, dosing the tanks of newly arrived fish with the stuff the same way people use "Stress Coat." I even find the smell pleasent.
What Melafix is not intended to do is cure serious disease. Any one of a number of "minor" surface infections can spread systemicaly, causing septic poisoning and organ damage. Nor does Melafix prevent re-infections, such as occures in major Ich infestations, where the environment is contaminated. Melafix is also not intended to de-contaminate the environment, so a fish that is suffering from nitrates or ammonia toxcity is not going to get "cured" by Melafix.
So people's success rate with Melafix will depend upon several factors as well, the most important one is "HAVE THEY DIAGONSED THE DISEASE CORRECTLY?" This is very rarely the case, seeing as how most "fungus" diseases are really bacterial infections, which is why anti-fungal medications don't work on them. Fortunately most medications in the fish world use broad spectrum poisons (copper sufate, formaldehyde, malachite green, etc) that kill most known fish parasites of the bacterial, fungal, or protozoan kind. So even with a mis-diagnosis, people will "cure" their fish because the medication they got is a "kill-all."
THE ONLY DIFFERANCE BETWEEN A MEDICATION AND A POISON IS THE CONCENTRATION. All medications are poisons when administered incorrectly. If any of you use Fontline or Advantix or Bio-Spot on your dogs and cats, you are in essense giving your animals the same insecticidal poisons farmers use in their fields. The difference being is the concentration, frequency of dose, and carrier mechanism. Same with fish. That's why it is very important not to chronically overdose fish tanks with medications. Effective levels kill the disease, overdoses kill the fish. Half the problem is that some people see "no effect" in the time frame they believe the fish should be "cured" (usually overnight and miraculasly), and just keep adding and adding medications, or worst off, mixing medications, which is only going to make the fish sicker in the long run.
Also people are faster to blame disease than environmental conditions. My theory on this is because of denial. People can't bare the thought that they themselves are responsible for their fish's illness simply because they are crappy aquarist, so they will readily blame some "unknown contaminate that is out of their control" rather than their own bad tank-keeping. Usually most fish "diseases" will clear up without the use of any medications once the water quality has been brought up to snuff, provided the immune system is not severely compromised. This could be why many people have had no success with Melafix. Treating fish diseases must be done in a holistic fashion, regardless of the medications used.
As far as the placebo effect and fish keepers, the analogy used before is correct, but I think the word you want is denial, not placebo. Most people will project what they want to see into their sick animal, I see it happen all the time at the veternarian's office where I work. If people want their animal to get well enough, they will say "Oh, Fluffy looks much better this morning" even if the animal looks like crap. Sometimes people project their own anxities into their pets as an "illness" even though the animal is fine. That doesn't mean a medication works because you want it to work, it just means that people are simply mental cases. People will believe that "Fluffy will be fine" even if the doctor gives Fluffy a shot of saline instead of medication, and may even project that Fluffy is better even if the animal is not. This is of course is completely medically unethical. But I have used the psycological benefits of the "placebo effect" on my kids at camp. I would give them "homesickness pills" that would make their homesickness go away. Of course, the "homesickness pills" were usually Good&Plenty's. Miraculusly, the homesickness would go away. Go figure.
For a placebo study to be completely valid, it must be done double blind, which means the researcher administering the pill doesn't know which is the medication and which is the placebo anymore than the test subject reciving the pill does. This eliminates the researcher's "powers of suggestion" which could plant cause and effect in the test subject's mind. Of course a third party keeps it all strait. A double blind study is more statistically valid than just a placebo study.
If anybody wants to post the active ingrediant of Melefix, I'll look it up in my pharmacy book and see what it is intended to use.
~~Colesea