Dropsy (pinecone) in fish — what it is, causes and odds of saving them
Raised scales, bloated belly, bulging eyes — not a disease in itself but a symptom of severe internal infection. Prognosis is grim: fewer than half survive even with correct treatment.
Dropsy ('pineconing') is not a disease in itself but a dramatic outward sign that the fish's internal organs are failing. It's most often a bacterial infection (Aeromonas, Pseudomonas, Mycobacterium), less often viral, parasitic, kidney failure or tumours. You don't treat 'dropsy' — you treat the cause.
Symptoms come in sequence: first the fish loses appetite and activity, then the belly swells, after a few days the scales begin to stick out perpendicular to the body — the classic 'pinecone'. Eyes bulge (pop-eye), fins clamp, swimming becomes laboured. By this point odds are already low.
Treatment protocol
Isolate in a 20–40 L hospital tank. Epsom salt 1–3 g/L helps reduce oedema by osmosis. Antibiotics: kanamycin 50 mg/L in the water + metronidazole 250 mg per 100 L in the water or in food, for 7–10 days. Keep water quality pristine — 25% changes every other day. Feed lightly — peas, daphnia, minimal portions.
Prognosis: with 'early' dropsy (belly bloated, scales still flat) 40–50% survive. With full pineconing, 10–20% survive. Prevention — quarantine new fish, varied quality food, no chronic stress, regular water changes. Sudden temperature swings trigger Aeromonas flare-ups.
FAQ
- If the fish already pinecones, is there any point treating?
- Odds are low, but not zero. If the fish is still eating and holding position — try the full antibiotic course. If it's already on its side and unresponsive — humane euthanasia with clove oil is kinder.
- Is dropsy contagious to other fish?
- Not on its own, but the pathogen (Aeromonas) is present in almost every aquarium. Healthy fish with strong immunity don't fall ill. The risk is to other already-weakened or stressed fish in the same tank.
- Do 'dropsy cures' from the fish store work?
- Most are herbal extracts with no proven efficacy. Only antibacterial drugs with a specific active ingredient (kanamycin, oxytetracycline, metronidazole) actually work.
Scientific board — ichthyologists and veterinarians
Ichthyologists and veterinarians with university degrees · Reference FishBase, Seriously Fish and peer-reviewed literature · Sign every reviewed article with their credentials shown
PhD in ichthyology, researcher of African Great Lakes cichlids
PhD in ichthyology, University of Edinburgh · Field research in Malawi, Tanganyika and Victoria (2013–2018) · 12+ peer-reviewed publications on cichlid behaviour
Sources
- Seriously Fish — Dropsy · Seriously Fish · 2026-05-31
- Practical Fishkeeping — Dropsy · Practical Fishkeeping · 2026-05-31