Hexamita is one of the most searched discus diseases, and probably the most common one I see. It’s an internal flagellate parasite that lives in the gut, and I’d bet almost all discus carry it and are never truly clear of it. Some fish just handle it better than others. It’s often the hidden cause behind weight loss and Hole in the Head.
Hexamita or Spironucleus?
You’ll see both names used. Hexamita is the traditional name, and it’s still what most forums, shops and medication labels call it. Research has since shown that the parasite found in discus is usually Spironucleus vortens, so that’s the more accurate scientific name. For discus keepers it makes no difference: the signs, causes and treatment are the same, so I use the name most people know.
Signs of Hexamita
- White, clear or stringy, jelly-like poo
- Losing weight, especially a thin forehead or hollow belly, sometimes while still eating well
- Spitting food out, then going off food altogether
- Darkening and hiding
- In longer-term cases, pits on the head (HITH)
What causes it
Low numbers of these flagellates are common in discus. Problems start when something weakens the fish and numbers multiply: poor water, a temperature drop, a move, bullying or a poor diet.
What to do
- Act early. It’s far easier to treat while the fish is still eating something.
- Move the fish to a hospital tank if you can, and keep the water very clean.
- Raise the temperature gradually to the top of the normal discus range and add extra aeration.
- Treat for internal flagellates. In the UK, the most effective treatment (metronidazole) is prescription-only, so speak to an aquatic vet. Treatments that can be soaked into food work best while the fish is still eating.
- Keep watching the poo after treatment. Normal, dark poo and a returning appetite are the signs it’s working.
How to prevent it
You probably can’t get rid of it completely, so the aim is keeping your fish strong enough that it never takes hold: stable, clean water, a varied diet, a well-sized group to reduce bullying, and quarantine for new arrivals.
Not sure what’s wrong?
Try the free Discus Health Checker. Answer a few quick questions and get the likely cause and what to do now. And grab the free guide, 7 Mistakes That Kill Discus Fish.
See all common discus health problems, and keep water quality high with easy discus water changes, the best prevention for most of them.
This is general guidance from experience, not veterinary advice. If fish are dying or you’re unsure, contact an aquatic vet.