Everything about treating a sick puffer follows from one fact: puffers have no scales. Medication crosses their skin far faster than it does a scaled fish, so standard doses of copper, formalin and some organophosphates can do more damage than the disease. On top of that, most large puffers are wild-caught and arrive carrying internal parasites. Quarantine and half-dose everything.
Common Puffer Diseases at a Glance
| Disease | Signs | First action |
|---|---|---|
| Ich (white spot) | Salt-grain white spots on body and fins, flashing | Raise temperature to 82°F, half-dose ich treatment, extra aeration |
| Internal parasites / worms | Thin fish that eats, white stringy faeces, sunken belly | Praziquantel or levamisole, then metronidazole |
| Fin rot | Ragged, receding, red- or white-edged fins | Large water changes; antibacterial only if it progresses |
| Cloudy eye | Milky film over one or both eyes | Test water; 50% change; check for injury |
| Flukes (gill and skin) | Flashing, rapid gilling, clamped fins, no visible spots | Praziquantel — well tolerated by puffers |
| Bacterial infection / ulcers | Red sores, open lesions, grey patches | Quarantine, clean water, half-dose antibacterial |
| Dropsy | Swelling with raised, pinecone-like skin | Poor prognosis; isolate, Epsom salt bath, review water |
| Constipation | Swollen belly, no faeces, still active | Fast 2–3 days, then feed shelled prey |
Symptom-indexed guides also exist for dwarf puffers, figure eight puffers and porcupine puffers.
Puffer Fish White Spots (Ich)
Ich looks the same on a puffer as on any fish — white spots the size of salt grains, plus flashing against decor — but the treatment differs.
- Raise the temperature to 82°F over 24 hours and add an airstone. This speeds the parasite's life cycle so the free-swimming stage is exposed to treatment sooner.
- Use a half dose of a malachite green or formalin-free ich product, or salt at 1 tablespoon per 5 gallons for freshwater species that tolerate it.
- Brackish species: raising salinity toward 1.010–1.012 is often enough on its own.
- Treat for the full course plus three days after the last visible spot; the parasite is only vulnerable between hosts.
- Never use copper on a puffer if any alternative is available.
Internal Parasites in Wild-Caught Puffers
Assume every wild-caught puffer — which means practically every fahaka, mbu, congo, hairy, figure 8, green spotted and Amazon puffer — has internal worms. The classic picture is a fish with a healthy appetite that stays thin, passing white stringy faeces.
- Quarantine every new puffer for four weeks in a bare tank with a cycled sponge filter.
- Praziquantel for flatworms and flukes, dosed in-tank, repeated after seven days.
- Levamisole for roundworms, with a large water change and gravel vacuum 24 hours after dosing.
- Metronidazole for protozoan infections, ideally in food if the fish is still eating.
- Feed well throughout. A dewormed fish needs to rebuild condition.
Fin Rot and Bacterial Problems
Fin rot in a puffer tank is usually a consequence of two things: nipped fins from a tank mate dispute, and nitrate that has been allowed to climb. Fix both before reaching for medication.
- Test ammonia, nitrite and nitrate. Change 50% of the water and repeat daily for three days.
- Remove or separate whichever fish is doing the biting — see the aggression page.
- If the edges are red or the erosion advances into the fin body, use a half-dose antibacterial in quarantine.
- Fins regrow clear and then re-pigment; expect several weeks.
Cloudy Eye
A milky film over the eye is a symptom, not a disease. In puffers the usual causes are poor water quality, a physical scrape (very common in a scaleless fish that rubs on decor), or a bacterial infection following one of those. Test the water, do a large change, remove sharp decor, and only medicate if the eye also swells or the fish stops eating.
The Puffer Quarantine Protocol
- Bare tank, cycled sponge filter, heater, one hiding place. Sized for the fish: 10 gallons for a pea puffer, 40 for a juvenile fahaka.
- Four weeks minimum. Observe feeding, faeces and breathing daily.
- Deworm in week one with praziquantel, then levamisole in week two if the fish is wild-caught.
- Do not medicate prophylactically for ich — watch instead, and treat if it appears.
- Match water parameters to the display tank, including salinity for brackish species, before moving the fish.
Test your parameters against the targets on the water parameters page or with the water parameter checker.
Frequently Asked Questions
Why does my puffer fish have white spots?
Salt-grain white spots with flashing against decor is ich. Raise the temperature to 82F with extra aeration and use a half dose of a copper-free ich treatment, because puffers are scaleless and absorb medication quickly. For brackish species, raising salinity to 1.010-1.012 often clears it alone.
Can you use copper on a puffer fish?
Avoid it wherever possible. Puffers have no scales and absorb copper rapidly, which causes skin damage and appetite loss. Use hyposalinity, chloroquine phosphate or praziquantel instead, depending on the parasite.
How do I treat internal parasites in a puffer?
Praziquantel for flatworms and flukes, repeated after seven days; levamisole for roundworms with a large water change and gravel vacuum 24 hours later; and metronidazole for protozoan infections. Assume every wild-caught puffer needs a course during quarantine.
Why does my puffer fish have fin rot?
Usually nipped fins from a tank mate dispute combined with rising nitrate. Test the water, do 50 percent changes for three days, separate the biting fish, and use a half-dose antibacterial only if the edges turn red or the erosion advances.
What causes cloudy eye in puffer fish?
Poor water quality, a physical scrape on decor, or a bacterial infection following either. Puffers have no scales and scrape easily, so test the water, do a large change, remove sharp decor, and medicate only if the eye swells or the fish stops eating.
How long should I quarantine a new puffer fish?
Four weeks in a bare tank with a cycled sponge filter, a heater and one hiding place. Deworm wild-caught fish with praziquantel in week one and levamisole in week two, and match water parameters to the display tank before moving the fish.