10 Common Betta Fish Diseases and How to Treat Them
Short answer: most betta disease is caused by poor water quality or stress. The first treatment is almost always the same: quarantine the fish, do a partial water change, and keep the water clean and warm. Only use medication for a confirmed diagnosis, and consult a vet when in doubt.
Health disclaimer: this is educational information, not veterinary advice. For a sick fish, a fish veterinarian is the most reliable option.
Prevention beats treatment
Healthy, unstressed bettas rarely get sick. The single most effective "treatment" is a cycled, warm (78–80°F), clean tank with regular water changes. A stressed fish in poor water gets sick; a healthy fish usually fights it off.
The 10 most common problems
| Condition | Signs | First step |
|---|---|---|
| Fin rot | Ragged, shrinking, blackened, or melting fins | Clean water + quarantine; medication if it spreads |
| Ich (white spot) | Tiny white salt-like dots on body and fins | Raise temp slightly + ich treatment; improve water |
| Velvet | Dusty gold/rust film, flashing against surfaces | Dim lights; velvet-specific treatment |
| Dropsy | Pinecone-like raised scales, swollen body | Quarantine; usually internal — vet advised |
| Swim bladder disorder | Floating, sinking, or swimming sideways/tilted | Fast 2–3 days, then feed daphnia; check for constipation |
| Popeye | One or both eyes bulging | Clean water + salt bath; vet if severe |
| Columnaris | Cottony white mouth or body patches | Antibiotic treatment; quarantine |
| Fungal infection | White cotton-like growths | Anti-fungal treatment; improve water |
| Ammonia burn | Red inflamed gills, gasping at surface | Immediate large water change; fix cycle |
| Constipation / bloating | Swollen belly, no appetite | Fast 2–3 days, then frozen daphnia |
The safe first-response routine
- Quarantine the sick fish in a separate small tank if you have one.
- Test and fix the water. Check ammonia, nitrite, and nitrate. Do a 25–50% water change.
- Confirm temperature is 78–80°F (25–27°C) — warm, stable water supports recovery.
- Feed lightly or fast — reduce food while the fish recovers.
- Treat for the specific diagnosis only after you've identified it. Never dump random medications into the tank.
When to get help: if the fish isn't improving within a few days, if it stops eating entirely, or for serious conditions like dropsy, consult a fish veterinarian. A wrong guess can do more harm than good.
Related guides: Color loss and fin rot · Happy vs stressed betta · Complete beginner guide