Troubleshooting: Fish
White spots on my marine fish: ich, velvet or something else?
White spots on the body or fins. Distinct salt-grain spots usually mean ich; a fine golden or white dust, often with fast breathing, suggests velvet.
Last checked . How we check
What should I check first?
- Look in good light, from the side: separate spots, or a dusty sheen?
- Count breaths: fast, laboured breathing is the warning sign.
- Which fish? A clownfish with peeling slime and fast breathing may have Brooklynella.
- Is the spot growing, or was it a speck of sand that has gone an hour later?
What is most likely causing it?
Most likely first. The order is our reading of how often the sources link each cause to this symptom.
- Marine whitespot (Cryptocaryon, ich). Separate white spots like grains of salt, coming and going over days. Tangs are the classic carriers (LiveAquaria).
- Velvet (Amyloodinium). Fine dust that is hard to see, fast breathing, hiding or hanging in the flow. It is often mistaken for ich and can kill within days.
- Brooklynella, in clownfish. Thick, peeling slime and fast breathing, most often in wild-caught clownfish (keeper reports, typical, check). A reason to buy captive-bred.
- Lymphocystis or other single growths. One or two cauliflower-like lumps that stay put, while the fish eats and breathes normally (our reading).
What should I do?
- For suspected velvet: move fish to a separate treatment tank and get help the same day.
- For ich: plan treatment in a separate tank. The display must then run without fish for long enough for the parasite to die out; keepers use about 70 to 76 days (typical, check).
- Treatments keepers use, all in a separate tank: copper (for ich and velvet), hyposalinity (ich only) and the tank transfer method, which moves fish to a clean tank every 72 hours (ich only). Protocols vary; follow the product label and test copper with a kit.
- Some fish tolerate copper badly: dwarf angels such as the flame angel, anthias, fairy wrasses and mandarins. LiveAquaria advises keeping copper under 0.15 ppm for flame angels.
- Feed well and keep the treatment tank water clean with frequent water changes.
What not to do
- Copper in the display: it kills snails, shrimp, crabs and starfish, and is hard to remove from rock and sand.
- Guessing at doses of medicines bought for other animals.
When should I get help?
Something dying right now? Go to the emergency playbooks.
Where do sources disagree?
| Topic | What sources say | Our reading |
|---|---|---|
| Copper and clownfish |
| Copper works but is risky: test it, do not overdose, and watch sensitive groups closely. |