Why is melafix useless? It was recommended to me by LFS (of course) but my fish was too far gone to help at that point. I still have it to use at a later date, but am still unclear of when to use it.
This is always a fun topic of discussion! First lets start with this "there is a clinical lack of evidence demonstrating the efficacy against bacterial, fungal or viral infections" (Clinical Microbiology Reviews,
Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties). Scientific evidence thus far has not demonstrated conclusively that the active ingredient works as suggested but that it does show some "promise" of antiseptic and antifungal activity. Its also worth noting that cajeput oil (the active ingredient in Melafix/pimafix/bettafix) is NOT soluable in water. The US patent for Melafix (patent #5882647) even clearly states this fact. The patent further suggests that the product must be 'vigorously shaken' in an aquarium setting to try and distribute it throughout the water column. Melafix's patent also states that there may be 'additional ingredients' in the product such as emulsifiers, preservatives, surfectants, defoaming agents and other 'adjuvants' that remain unnamed.
Its worth noting that the American Cancer Society and the Mayo Clinic specifically warn of the toxicity of the active ingredient to both humans and pets, including but not limited to rash, weakness, dizziness, drowsiness, confusion, vomiting, blood cell abnormalities, coma and death. There are a few anecdotal studies that go on to suggest that the products of the oil's breakdown into into metabolites can cause liver damage in fish or the product can interfere with proper respiration. Likewise, there are other anecdotal studies that suggest that melafix may be helpful in certain situations.
Personally, I feel adding a product of questionable efficacy, unknown ingredients and that 'may' cause potential harm is not the wisest decision. Unhealthy water is responsible for the largest portion of fish ailments- addressing this should be a priority. Quaratining new fish to prevent the spread of disease and treating with an appropriate medication warranted by the situation along with healthy water is paramont to a positive prognosis. Do your own research and make your own decisions before adding anything to your aquarium.