Identify it by symptom
| What you see | Likely cause | First step |
|---|---|---|
| White salt-grain spots on body & fins | Ich (white spot) | Raise temp slowly, treat, check water |
| Fuzzy, tufted white growth on a reddened base | Epistylis (often mistaken for ich) | Antibacterial approach, not salt |
| Ragged, receding, or milky fins | Fin rot (bacterial) | Improve water quality first |
| Cotton-wool white patches | Fungus | Isolate, antifungal |
| Swollen belly, scales sticking out ("pinecone") | Dropsy (internal, serious) | Quarantine; often a late-stage sign |
| Gold/rust dust, flashing, clamped fins | Velvet (serious, fast) | Treat urgently, dim lights |
| Gasping at surface, rapid gilling | Ammonia/nitrite or low oxygen | Test water, big water change now |
| Flashing/scratching with no spots | Gill flukes or early parasite / irritation | Test water, observe closely |
Why the symptom alone isn't enough
Lots of diseases look alike — ich and epistylis are the classic mix-up, and treating one as the other wastes days you don't have. More importantly, most outbreaks start with a water-quality trigger: an ammonia spike, a nitrate climb, a temperature swing, or stress from incompatible tankmates. Treat the disease and ignore the cause and it comes right back.
What to always do first
- Test the water — ammonia, nitrite, nitrate, pH, temperature. A surprising number of "diseases" are poisoning.
- Do a water change — it's the safest first move for almost any problem.
- Quarantine visibly sick fish if you can, before medicating the whole tank.
- Change one thing at a time and re-check, so you know what worked.
Let an AI read it against your water
Instead of guessing from a chart, TankMate lets you photograph the fish and get a plain-English read on the likely problem — cross-referenced with your tank's logged water tests, so it catches the water-quality cause, not just the visible symptom. You get concrete next steps, not a diagnosis in a vacuum.