No, I'm not going to lecture you. Nor anyone else. Maracyns are different meds I think. I know one is erythromycin which of course is an antibiotic. Fungus is a word too loosely used to describe white on a fish. And of course Columnaris is often called fungus when in reality it is a bacterium.
My concern is,,as is with many people, the arbitrary dose of these antibiotics that aquarists have been conditioned to use.
Let's look at Maracyn. It is labelled erythromycin which is a broad spectrum antibiotic used to primarily treat gram negative bacteria. The instructions say to use one tablet per ten gallons of water. Okay, that's easy. So what is the dose for a fish? Every fish is different when it comes to osmotic activity. Fish are all different when it comes to weight, metabolism, etc. So how is dumping a tablet in 10 gallons of water medicating anything by a weight/milligram dosage. It is not. It is a shot in the dark.
Now, what is happening in your tank when you add these broad spectrum antibiotics?
They are not just affecting your fish but everything in your tank. The bacteria that cause disease problems exist naturally in your tank and all around you. And when we just arbitrarily use these antibiotics they can kill some bacteria, and more importantly can cause some to become resistant to these antibiotics.
If you can get your hands on a february edition of Freshwater And Marine Aquarium magazine(Fama), there is a great article by Dr Mark Mitchell DVM on treating fish. He goes into more detail about how fish can be effectively treated with medications and the one way they cannot be effectively treated is by dumping things in the water.
Incidentally, the federal government is finally taking a close look at the aquarium industry's chemical additives including antibiotics. And finally hopefully there will be some control over uses for this.
It is easily out of the scope of most aquarists to properly diagnose diseases without cultures. Certainly most aquarists cannot identify a bacterium and choose the proper antibiotic and properly administer it to a fish based on weight/milligrams.
All any of us can do is go to the store and buy a box of something and trust it will work. And the problem with this is that there are no regulations controlling what is sold and there are no regulations in place to force product labels to tell the truth.
Fixing problems in fish should be more about fixing the habitat and the water parameters so that the fishes' immune system can fix the problem.
Unless an aquarist can identify specifically what is wrong with a fish, and can dose the appropriate medication to that fish in an effective way then we are all creating hazards not only in the tank, but into our homes and environment.
Bill