Metronidazole (MNZ) is a very popular and effective antiprotozoal medication in aquarium and ornamental fish industry which is used to treat a vast variety and range of both internal and external protozoan infections and parasites (not worms) in discus and other tropical fish. Other than a strong and reliable antiprotozoal drug, metronidazole is also an antibiotic medication that can treat Anaerobic bacterial infections. Other brand names of the same drug are Flagyl, Metrogel, Noritate, and MetroCream. However, flagyl is more common to be found than other brand names in the US market.
How to use Metronidazole to treat Discus Fish
When it comes to discus fish, the metronidazole plays an important role in all quarantining new fish, prevention, and treatment processes. Flagyl is mostly used to treat different kinds of flagellates and Internal protozoan parasites such as hexamita, external protozoan infections like Spironucleus which causes hole in the head & head and lateral line disease , Anaerobic bacterial infections, digestive and intestinal disorders, and etc.
Dosage & Administration
Before I go over Flagyl dosage, administration, and frequency, I would have to say that It really depends on circumstances and can vary case by case. By the way, there is no consensus among researchers, breeders, hobbyists, ornamental fish distributors, and etc and that is why there are so many different doses and administration routes for Metronidazole. In the next paragraph, you will learn how to treat discus with Metronidazole.
According to what I have read, learned, and experienced over the past years and also my personal opinion, the standard and the most effective dosage for the metronidazole, especially in a discus tank is 250 mg per 10 gallons of water every other day for up to 4 days with at least 50% water change before each dose. Keep in mind that at least a minimum of 3 doses is necessary to eliminate the newly hatched larvae of the parasites and that is because the eggs from parasites are not affected by Noritate; So that, although most of the live parasites will die rapidly right after the first dose of the medicine, the parasites eggs will be hatched couple of hours later.
Medicated Food & Doses
Metronidazole also can be used in fish food to improve the treatment effects. However, not in all cases the internally sick fish Having said that, treating discus fish with metronidazole is being done by different and sometimes weird doses some of them which are much stronger than discus liver can handle.
Metronidazole-Based Fish Medications
Human Metronidazole powders and tablets are not so water soluble and without using proper excipients and/or solvents, it is very unlikely that the drug will be effective, unless it is used in a medicated food. It is highly recommended to use an aquarium/fish medicine as they are very water soluble. Fish medications such as Fish Zole™ from Thomas Labs and Seachem MetroPlex™ are some of the best fish medications with active ingredient of Metronidazole.