Koi Quarantine: The Habit That Protects Your Whole Pond

Ask a room of longtime koi keepers what they’d tell their beginner selves, and quarantine wins by a landslide — usually with a story attached.

Why this matters more with koi than other fish

Two reasons. First, the stakes: a stocked koi pond can represent years and thousands of dollars, and koi live decades. Second, one pathogen in particular — koi herpesvirus (KHV) — can kill an entire pond in two weeks, and surviving fish carry it silently for life. There is no cure. The only defenses are dealer screening and your own quarantine.

The simple quarantine setup

You don’t need a second pond:

• 100–300 gallon tank (a stock tank works) with a cycled sponge filter or media borrowed from your main filter
• Cover or net — new koi jump
• Heater to hold 68–75°F: warm water makes latent disease show itself, which is the point
• Its own net and equipment — nothing shared with the pond

Run 2–4 weeks. Watch appetite, breathing rate, and skin daily; feed lightly (what koi eat covers amounts). If anything appears — ulcers, flashing, gasping — you’ve contained it to one tank, which is the entire victory.

The questions to ask a dealer

A dealer’s quarantine practice is the best proxy for how seriously they take fish health:

1. “How long do you quarantine incoming fish before selling?”
2. “Do you test for KHV?” (Especially important with imported fish.)
3. “What’s your health guarantee if a fish arrives sick?”

Every FindKoi dealer profile lists the quarantine protocol and health guarantee the dealer states publicly — profiles marked “not stated” are exactly where to ask these questions yourself before paying. It’s also fair to weigh it into what you pay; the price guide assumes healthy, screened stock.

When quarantine ends

Match temperatures between tank and pond, transfer the fish (not the water), and watch closely for another few days. Then enjoy the small smug pleasure of having done it right — it compounds for 25 years.