by Carol Roberts

These treatments are ones that I have used successfully. They are effective and fairly safe. The medications are readily available and simple to use.

Intestinal Flagellates

Symptoms:  Your discus may quit eating or spit out its food. White, stringy, mucus-like feces will hang like a thread from the anus.

Your discus may be dark in color and stay in the back of the tank away from the other discus.

Treat with Metronidazole sold in pet stores as Hex-A-Mit or Metrozol.  Can be purchased online from several sources. The most effective dose is 400 – 500 mg per 10 gallons of water. A water temperature of 92+ degrees should be maintained throughout treatment.  Dose metronidazole each day after a 50% water change for 3 to 5 days.  Water used for water changes should be close to 92 degrees.  During treatment feed the discus sparingly of favorite foods like frozen bloodworms. Keep water temperature elevated for a week after treatment ends.  It may take a week or so for the discus to regain it’s appetite.  In severe cases of long standing disease you may need to dose metronidazole every 8 hours for three days. It is safe to dose all fish in tank or you can remove the affected fish and treat them in a smaller hospital tank. Metronidazole will not hurt your bio-filter.

Bloat or Constipation

Symptoms: Your discus will look bloated – like he swallowed a marble.  There may be an indentation behind the bloated area as if he had been pinched by your thumb and forefinger.  Your discus may shimmy and shake.  He may not be able to maintain his balance and will generally look uncomfortable and be dark in color.

Treat with Epsom Salt (Magnesium Sulfate – sold in grocery stores or drug stores as a foot soak for people). Use one or two teaspoons of Epsom Salt per 10 gallons of water. Your Discus should be better in 4 hours or you can add another dose. Epsom salt will not hurt the filter or the other fish.  You may dose in higher amounts of even one or two tablespoons per 10 gallons.  If your fish is not better in 24 hours suspect a bacterial infection.

Epsom Salt is Magnesium Sulfate.  Table salt is Sodium Chloride. Both can be found at your local grocery store. Metrozol is sold through online fish catalogs.

This bloated discus is suffering from an internal bacterial infection.
The highlighted area shows thick pus exuding from the vent.

Gill Flukes or Bacterial Disease

Symptoms:  Your discus may breath rapidly. Gills may be flared. He may be dark in color and stay apart from the other discus.  Head may be pointed down at a 45 degree angle.

Treat with Formalin (formaldehyde) sold in pet stores as Formalin and in a combination with dyes as Quick Cure and Rid Ick or can be purchased online.  I dose One cc or ml per 10 gallons of water. Do a 50% water change 8 hours after adding the Formalin.  Do not raise temperature.  Add extra air as Formalin depletes oxygen.  If you see an improvement (less scratching/easier breathing) after the first dose you can continue treating every other day for two weeks.  Dose all fish in the tank.  Formalin may impact the bio-filter.

Medications I use for external parasites include Formalin, Quick Cure, Fluke Tabs, and Parasite Clear.  Praziquantel is a white powder that kills flukes and tapeworms.


Symptoms: Little, skittery bugs you can barely see skitter and hop on the bottom of the tank and inside the filter. They are a symptom of overfeeding.

Treat with Fluke Tabs sold in pet stores or online. Make sure inside of tank and filters are clean. On day one do a 50% water change and dose one tablet per 10 gallons of water. Day two and three do regular water changes. Day four dose one tablet per 10 gallons.  Parasite Clear will also work and is sold at Wal-Mart. Follow package directions.


Symptoms: White dots on the glass walls of the tank and inside the filter. Planaria love smooth surfaces.

Treat by cleaning your tank, rinsing the filter, wiping down the inside of your tank and increasing water changes.  Decrease amount fed and use a prefilter if food and feces are being sucked into the filter.  You can also dose with Formalin at 1 cc per 10 gallons, but you would need to watch for ammonia spike if heavy die off.

For more information on discus diseases and online help visit the Simply Discus forum by clicking the link or by clicking on the banner below.