About Angelfish Medications – What is the Best Treatment for Your Sick Angelfish?

Bacteria, parasites, and fungi are the primary causes of diseases in all fish, including angelfish. Fish medications are formulated to address one or all of these conditions.  It’s best to try to determine the specific angelfish disease, and precisely treat it.

This is a list of the common fish medications you may need for your angelfish and other tropical fish that will treat most common angelfish ailments. As with any medication, read and follow the instructions. Note if the medication has side effects such as killing bacteria in the biological filter system or plants. Doing a partial water change rarely hurts, so do water changes before and after treatment. Remember to remove the charcoal filters when treating. It is generally best to set up a hospital tank for treatment.


Metronidazole is used for parasites, such as Hexamita, and some bacterial diseases. For treatment of Hexamita in angelfish, author Ed Stansbury in Breeding & Raising Angelfishes, recommends only using metronidazole if necessary as other medications may contain arsenic that may temporarily sterilize the adult angelfish.

Formalin/Malachite Green Formula

A formalin/malachite green mixture is recommended by many fish experts as being the best treatment for external parasites, such as ich or velvet disease, and fungal infections. It can also be helpful in treating fin rot in angelfish. QuICK Cure is a commonly used and cheap formalin/malachite green fish medication formula.

Antibiotics for Angelfish

Bacterial infections in any fish are difficult to diagnose and treat. Mouth rot, fin and tail rot, and skin ulcers can be a sign of an external bacterial or fungal infection. Internal bacterial infections can cause emaciation and pale coloring. External bacterial infections in fish are easier to treat because getting the antibiotic inside the fish to be effective is extremely difficult.

Using any antibiotics increases the likelihood of your fish tank developing antibiotic resistant bacteria and killing the helpful bacteria in your tank. If you must use an antibiotic, use it exactly as directed and move the sick fish to a hospital tank. Also, if you need to use an antibiotic again in the future, don’t use the same one. Rotating antibiotic types will help prevent the development of antibiotic resistant bacteria in your aquarium.

To provide more effective antibiotic treatment for fish, antibiotics that are known to better absorb into the fish tissue are best. Mardel makes Maracyn-Plus, a combination of trimethoprin and sulfadimidine mix with chitosan. The chitosan is synthetic mucus that binds the medication directly to the fish’s skin.

Mardel also makes Maracyn-Two which contains minocycline as the active antibiotic. Minocycline is known to better absorb into the tissue of fish.

Know that treating fish can be a hit or miss proposition. Unless diagnosed by a veterinarian, the ailment may not be what it seems, and even vets can make mistakes. Some of these fish medications may work well in one tank, but be a disaster in others. If you must use a medication for your angelfish, you should first positively identify the disease as best you can, use medication that targets that disease, and use only the medication you need.