Betta fish diseases look frightening, but most of them follow a pattern: something in the tank goes wrong first (dirty water, cold water or stress), and the illness follows. This page is the starting point for any sick betta. Use the symptom checker to find the likely problem and how urgent it is, follow the three first steps that apply to every case, and use the medicine table so you do not reach for the wrong bottle.
Betta Symptom Checker
Find the closest match to what you see, then open the full guide for the step-by-step treatment.
| What you see | Likely problem | How urgent |
|---|---|---|
| White salt-grain spots on body and fins | Ich (white spot) | Within a day |
| Gold or rusty dust sheen, seen best with a torch | Velvet | Same day |
| Ragged, shrinking or dark-edged fins | Fin rot | Within a day |
| Floating, sinking or swimming on its side | Swim bladder or constipation | Within a day |
| Scales sticking out like a pinecone | Dropsy | Urgent |
| One or both eyes bulging | Popeye | Within a day |
| Flat greyish patch or cotton-like mouth that spreads fast | Columnaris | Urgent |
| Fluffy white tuft on a wound | Fungal infection | Within a day |
| Red streaks under the scales | Septicemia | Urgent |
| Thin body, stringy white poop, eating normally | Internal parasites | Within days |
| Fins held tight against the body | Clamped fins (a warning sign) | Test water today |
| Gasping at the surface, red gills | Ammonia or nitrite poisoning | Urgent |
| Horizontal stripes, hiding, faded colour | Stress | Find the cause |
| Lying still, barely responding | A betta in serious decline | Urgent |
First 3 Steps for Any Sick Betta
- Test the water. Ammonia and nitrite should be 0 ppm and nitrate under 20 ppm. A liquid test kit is more reliable than strips; see the best betta water test kits.
- Check the temperature. It should be a stable 78–80°F. Cold water is behind many ich and fin rot cases; see ideal betta water temperature.
- Fix the water before you medicate. Do a 25–30% water change with dechlorinated water at the same temperature. Many mild cases improve from clean, warm water alone.
Isolate the betta in a hospital tank if it shares the tank with other fish, or if the medicine could harm plants, snails or shrimp.
Which Medicine for Which Problem
The wrong medicine at the wrong dose harms more sick bettas than many of the diseases themselves. Always dose by the real water volume, remove carbon from the filter while medicating, and do not mix treatments unless the label says it is safe.
| Product | What it is | Used for | Typical use |
|---|---|---|---|
| Aquarium salt | Sodium chloride | Mild external problems, early fin rot, ich support | About 1 tsp per gallon for treatment, for no more than about 10 days |
| Epsom salt | Magnesium sulfate | Constipation, swim bladder, dropsy, popeye | About 1 tbsp per gallon as a 10–15 minute bath |
| Antibiotic (e.g. kanamycin, minocycline) | Antibacterial | Severe fin rot, columnaris, septicemia, dropsy | Follow the label exactly for your gallons |
| Antifungal (e.g. methylene blue) | Antifungal | True fungus (fluffy white tufts) | Follow the label; confirm it is not columnaris first |
| Anti-parasite medicine | Antiparasitic | Velvet; internal parasites (often in food) | Follow the label; velvet also needs the tank kept dark |
| Table salt | Iodised salt with additives | Nothing | Never use it in a fish tank |
When not to medicate
Do not medicate for clamped fins, faded colour or a fish that is “just hiding” until you have tested and fixed the water. These are usually signs of stress or poor water, not infection. Also avoid human antibiotics: the doses are wrong for fish and can do more harm than good.
How to Prevent Betta Diseases
Prevention is far easier than treatment. Nearly every disease on this page traces back to one of seven habits being skipped:
- A fully cycled tank, so ammonia never builds up. See how to cycle a betta tank.
- Stable heat of 78–80°F with an adjustable heater.
- Enough water. At least 5 gallons, because small tanks swing fast. See the betta tank size guide.
- Weekly partial water changes of 20–30%. See how often to clean a betta tank.
- Small meals and a weekly fast day. See how much to feed a betta.
- Quarantine every new fish, plant and live food source. See how to quarantine a new betta.
- Low stress and a daily look. Know what normal looks like; see signs of a healthy betta.
| How often | Task |
|---|---|
| Daily | Quick health check; remove uneaten food |
| Weekly | Test the water; 20–30% water change; one fast day |
| Monthly | Check the heater and filter; full parameter check |
| Every new addition | Quarantine for 4–6 weeks |
| Parameter | Target | Why it matters |
|---|---|---|
| Ammonia | 0 ppm | Burns gills and fins and weakens immunity |
| Nitrite | 0 ppm | Stops the blood carrying oxygen |
| Nitrate | Under 20 ppm | High levels cause slow decline |
| Temperature | 78–80°F, stable | Cold or swinging water triggers ich and weakens immunity |
| pH | About 6.5–7.5, stable | Stability matters more than the exact number; see betta pH |
| Chlorine | 0 (always use conditioner) | Damages gills and kills filter bacteria |
When a Betta Keeps Getting Sick
If the same illness comes back, the medicine was treating the symptom while the cause stayed in the tank. Check the usual suspects in order: an uncycled or overstocked tank, a heater that swings, overfeeding, sharp decorations tearing fins, and new fish added without quarantine. Fix the cause and repeat infections usually stop.
Sources & Further Reading
Merck Veterinary Manual, fish health and water quality; University of Florida IFAS Extension, fish disease and quarantine fact sheets; Seachem and API product instructions for dosing; the individual disease guides linked above.
Frequently Asked Questions
What are the most common betta fish diseases?
Fin rot, ich (white spot), swim bladder problems from constipation, velvet, dropsy, popeye, columnaris and fungal infections. Most start with poor water quality, cold water or stress.
How do I know if my betta is sick?
Look for clamped fins, faded colour, hiding or lying on the bottom, refusing food, white spots, a gold dust sheen, ragged fins, bloating or scales sticking out. Any change from normal behaviour that lasts more than a day is worth checking.
What should I do first when my betta looks sick?
Test the water for ammonia, nitrite and nitrate, check the temperature is 78-80F, and do a partial water change if anything is off. Then match the symptoms to the chart before using any medicine.
What is the difference between aquarium salt and Epsom salt?
Aquarium salt is sodium chloride and supports mild external problems such as early fin rot or ich. Epsom salt is magnesium sulfate and draws out fluid, so it is used for constipation, swim bladder problems, dropsy and popeye. They are not interchangeable.
Can betta fish recover from disease?
Yes, most do when the illness is caught early and the water problem behind it is fixed. Fin rot, ich, constipation and mild popeye usually recover well. Dropsy and advanced columnaris are much harder to treat.
How can I prevent betta diseases?
Keep a cycled tank, a stable 78-80F, weekly partial water changes, small portions with a weekly fast day, and quarantine any new fish or plants for a few weeks.