What does Carp pox (Cyprinid herpesvirus 1 (CyHV-1)) look like?

White/grey waxy patches. Tumor-like lump. Patches on fins + body.

How is Carp pox (Cyprinid herpesvirus 1 (CyHV-1)) treated?

No treatment needed: Carp pox is mostly cosmetic. Growths regress at 75°F+. Most pond keepers do nothing.

POND disease

Carp pox (Cyprinid herpesvirus 1 (CyHV-1))

Reviewed by the Fast Aquatics husbandry team · Updated May 2026

Quick referenceCarp pox is a viral skin disease causing waxy white-grey growths on koi + goldfish. Generally non-lethal; growths regress in warm summer water and recur in cool seasons.

Symptoms

White/grey waxy patches
Tumor-like lump
Patches on fins + body
No behavioral change

Cause

Cyprinid herpesvirus 1 (CyHV-1). Latent infection that flares in cool water (under 65°F) + recedes in summer warmth. Common in mass-bred koi.

Treatment options

No treatment needed. Carp pox is mostly cosmetic. Growths regress at 75°F+. Most pond keepers do nothing.
Warm water. Move fish to indoor system at 75°F for 4-6 weeks. Growths typically fade.
Improve nutrition. High-quality protein + vitamin C in diet supports immune response.
Surgical removal. Only for valuable show koi with disfiguring growths. Veterinary procedure under MS-222 anesthesia.

Always treat in a separate quarantine or hospital tank. Most medications are toxic to coral, invertebrates, and live rock biology. Consult an aquatic veterinarian for valuable fish.

Prevention

Buy koi from CyHV-1-clean breeders. Maintain warm water (above 70°F) for sensitive show koi.

Fatality + outcome

Almost never lethal. Cosmetic; reduces show value.

Full disease database · Symptom matcher · Q&A library · Glossary · QT timeline calculator

Aquarium-keeping fundamentals

Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.

Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.

Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.

Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.

Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.

Frequently asked questions

How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.

What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.

How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.

Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.