The Complete Guide to Koi Quarantine: Everything You Need to Know

By KoiQuanta Editorial Team|Updated Mar 2026

Disease introduced without quarantine spreads to the display pond in 80% of cases within 14 days. That figure defines the stakes of quarantine management better than any other single data point. A fish that looks perfectly healthy on arrival can be incubating Koi Herpesvirus, carrying Dactylogyrus on every gill arch, or hosting early-stage Aeromonas infection that manifests as ulcers 10 days after it enters your pond.

Quarantine is the management system that intercepts those introductions before they reach your collection. This guide covers every aspect: setup, protocols, disease management within quarantine, record keeping, and discharge criteria.

KoiQuanta is the only tool that manages the complete quarantine workflow described in this guide. No competitor has a single quarantine resource built into a management platform.

TL;DR

A single 60cm koi needs at minimum a 300-litre quarantine tank.
Alternatively, seed a new filter with established filter media, bacterial supplement products, and an ammonia source (pure ammonia without surfactants or a piece of raw shrimp) and cycle over 3-4 weeks before first use.
A heater that can maintain stable temperature within 2-3°C of your display pond is essential.
Introduce water from your quarantine tank to the transport water gradually over 10 minutes before releasing the fish.
Feeding should begin on day 2-3, once the fish has settled.
A fish not eating within 3-5 days of arrival warrants investigation.
It will naturally break down over 3-5 days.

Part 1: Why Quarantine Matters

The Biology of Disease Introduction

Most koi pathogens don't announce themselves. A fish carrying Trichodina, Gyrodactylus, or Dactylogyrus shows no visible signs at all. A fish in the early stages of bacterial ulceration has skin changes so subtle they're invisible at the surface. A KHV-incubating fish looks and behaves normally for days to weeks before the disease becomes clinically apparent.

This is what makes visual inspection inadequate as a disease prevention measure. You cannot tell by looking at a koi whether it's carrying pathogens that will kill your other fish.

Quarantine works by holding the fish in isolation long enough for:

Any incubating disease to manifest and be detected
Prophylactic treatments to eliminate the most common parasites
The fish to demonstrate sustained health before entering your collection

The Cost of Not Quarantining

A single KHV outbreak in a collection with high-grade Japanese koi valued at £1,000 each and 70% mortality produces losses in the tens of thousands of pounds. A Trichodina introduction from an unquarantined fish can trigger a treatment event and secondary bacterial infections across your entire pond, costing hundreds to thousands depending on collection value.

The annual cost of maintaining a quarantine system - equipment, medications, and software - is predictable and bounded. The cost of a disease introduction is unpredictable and potentially catastrophic.

The insurance logic is straightforward. You don't insure your house because you expect it to burn down; you insure it because the cost of it burning down is catastrophic relative to the cost of the premium. Quarantine is the same principle applied to your koi collection.

Part 2: Setting Up a Quarantine System

Quarantine Tank Requirements

A functional quarantine setup requires:

Tank size: 300-1,000 litres is appropriate for most hobbyist quarantine. The tank must be large enough for the fish to swim freely without crowding. A single 60cm koi needs at minimum a 300-litre quarantine tank. Multiple fish or larger fish need proportionally more volume. Overcrowding in quarantine increases stress and disease risk.

Filtration: A biological filter is needed to process ammonia from fish waste. This is the most important consideration in quarantine setup. A sponge filter with an air pump provides both biological filtration and aeration in one unit - the standard recommendation for quarantine tank filtration.

The filter must be cycled before fish arrive. Running an established sponge filter from your main pond in the quarantine tank immediately provides working biological filtration. Alternatively, seed a new filter with established filter media, bacterial supplement products, and an ammonia source (pure ammonia without surfactants or a piece of raw shrimp) and cycle over 3-4 weeks before first use.

Aeration: Separate from the filter, additional aeration is helpful during treatments (some medications reduce dissolved oxygen) and during disease events (stressed fish need high oxygen). An air stone or additional air pump is a small investment with significant value.

Heater: Koi are kept in temperature-controlled quarantine for several reasons. A heater that can maintain stable temperature within 2-3°C of your display pond is essential. Sudden temperature changes stress fish. Stable temperature also controls the quarantine environment for KHV risk assessment - maintaining fish in the KHV-active temperature window (16-25°C) during quarantine helps reveal KHV infection that might be latent outside this range.

Thermometer: Digital thermometers are accurate and affordable. Don't rely on heater dials for precise temperature.

Cover: Koi jump. Quarantine tanks at floor level or filled close to the top must be covered or netted to prevent losses.

Equipment and Supplies

Stock these before fish arrive:

Testing equipment:

Ammonia test kit (daily testing during quarantine)
Nitrite test kit
pH test kit (twice weekly during quarantine)
KH test kit (weekly)
GH test kit (weekly)
Thermometer

Medications:

Non-iodized salt (10+ kg for a 1,000L quarantine tank at 0.3%)
Praziquantel (for prophylactic fluke treatment)
Potassium permanganate (for diagnostic assessment and treatment)
Basic antibiotic supply (discuss with your fish vet - oxytetracycline or similar)

Other supplies:

Dedicated net (never shared with display pond)
Dedicated bucket
Dechlorinator (sodium thiosulfate or commercial dechlorinator)
Record keeping system (KoiQuanta or a dedicated notebook)

Isolation From Your Main Collection

Physical separation is not optional. The quarantine system must be isolated from your display pond:

Separate equipment that never contacts the display pond
No shared water circuit between quarantine and display
No splash or spray contact between systems
Ideally, the quarantine tank is in a separate physical location from the display pond

The most common quarantine system failures involve physical proximity between the quarantine tank and the display pond that allows water contact through splash, spray, or shared equipment.

Part 3: The Standard Quarantine Protocol

Day 1: Fish Arrival

When a new fish arrives:

Acclimate before introduction. Float the bag or container in the quarantine tank for 15-20 minutes to equilibrate temperature. Introduce water from your quarantine tank to the transport water gradually over 10 minutes before releasing the fish. This helps acclimate the fish to your water chemistry.

Don't introduce the bag water to your quarantine tank. The bag water has been in contact with the seller's facility. Release the fish, not the water.

Observe for 30-60 minutes. Normal arrival behaviour is initial exploration and some wariness. Fish hanging at the surface, showing laboured breathing, or swimming erratically need immediate assessment.

Log the arrival in KoiQuanta with the fish details, source, date, and initial observations.

Days 1-7: Observation and Acclimatisation

Test ammonia daily. New fish in a new environment may show elevated ammonia from stress-related metabolism. Nitrite should be zero in an established quarantine filter. pH should be checked every 2-3 days.

Daily observation should be logged. What is the fish doing? Is it eating? Is it swimming normally? Are there any signs - flashing, fin clamping, mucus changes, colour changes?

Feeding should begin on day 2-3, once the fish has settled. Start with small quantities and observe whether the fish eats. A fish not eating within 3-5 days of arrival warrants investigation.

Don't start prophylactic treatment immediately - wait until the fish has settled for 5-7 days. Treatment adds stress on top of transport stress in an already stressed fish.

Days 7-10: First Praziquantel Dose

At approximately day 7 (adjust based on the fish's condition and settling time), administer the first praziquantel treatment.

Dosing: 2 mg/L (2 ppm) of praziquantel in the quarantine tank. Dissolve the praziquantel in a small volume of hot water before adding it to the tank to ensure even distribution.

Praziquantel is specific to monogenean parasites (Dactylogyrus and Gyrodactylus). It won't harm the fish at therapeutic doses and is safe for biological filter bacteria at this concentration.

Leave the praziquantel in the tank - don't perform a water change to remove it. It will naturally break down over 3-5 days.

Continue salt at 0.3% if you've been using it. Salt during quarantine reduces osmotic stress and provides some inhibition of ectoparasites.

Day 21: Second Praziquantel Dose

The second praziquantel dose addresses any Dactylogyrus that were developing during the first dose (flukes have a life cycle that makes a single treatment insufficient).

The timing of day 21 is important - don't skip or significantly delay this dose. A fish that looked healthy after the first dose may have had developing parasites that the first dose didn't kill because they weren't yet in the vulnerable stage.

If you observed any signs of parasite infection after the first dose, the second dose is even more important.

Weeks 1-6: Daily Observation

The most important component of quarantine is observation. The protocol structure (treatments, parameter testing) is the skeleton; observation is the muscle that actually catches disease events.

Daily observation means looking at each fish for 2-3 minutes and assessing:

Behaviour:

Is the fish swimming normally? Normal koi swim actively, position themselves at comfortable depths, and respond normally to your approach.
Is the fish eating? Active feeding is the strongest single indicator of fish health.
Is the fish flashing or rubbing? Even a single flash is worth noting. Multiple flashes in a day warrant closer attention.
Is the fish isolating? A fish that hides, sits on the bottom, or hangs at the surface without obvious reason is showing a sign.

Physical:

Fin position (clamped fins are a stress or disease sign)
Skin and scale condition (new lesions, redness, scale lifting)
Eye condition (cloudiness, swelling)
Gill movement (breathing rate and symmetry)
Mucus coat (excessive mucus suggests irritation)

Log every observation in KoiQuanta. Even "all normal" observations matter - they establish the baseline that makes deviations visible.

Part 4: Managing Disease Events During Quarantine

When a Fish Shows Signs

A fish showing disease signs during quarantine is exactly what quarantine is designed for. You caught it before it reached your display pond.

Don't panic. A fish showing signs in quarantine is in the right place.

Investigate before treating. What signs are present? Is it one fish or all fish in the tank? Did anything change in the past 24-48 hours (water quality, feeding, temperature)?

Test water quality before attributing signs to disease. Many "disease" presentations in quarantine are water quality events.

Consider the likely pathogen. Flashing suggests ectoparasites. Clamped fins suggest systemic stress. Lesions suggest bacterial infection. Match the investigation to the likely cause.

Consult the koi disease reference manual for differential diagnosis. For unusual presentations or rapid deterioration, contact a fish veterinarian.

Extending Quarantine for Disease Events

Any fish that has a disease event during quarantine has its quarantine extended. The quarantine period counts from the resolution of the disease event, not from the original arrival date.

If a fish has a fluke infestation treated at week 3, the 7-day clean observation period resets from the resolution of the treatment. The fish may need a total of 8-9 weeks in quarantine rather than 6.

This is correct and important. A fish that has had a disease event during quarantine has a higher risk profile than a fish with a completely clean quarantine. The extended observation period confirms resolution before discharge.

Part 5: Record Keeping in Quarantine

Why Records Are Essential

Records serve multiple functions in quarantine management:

Disease detection: A record of daily observations creates a baseline. When you look back at a fish that has just shown signs, you can see whether the signs developed gradually (suggesting chronic disease progression) or appeared suddenly (suggesting acute event).

Protocol compliance: Records confirm that scheduled treatment doses were administered, that testing happened on schedule, and that observations were made as required. They make "I think I did the day 21 dose" into "I confirmed the day 21 dose at the correct dose on day 21."

Supplier quality analysis: Linking quarantine outcomes to fish sources over multiple purchase events reveals which suppliers produce higher-risk fish. This analysis is only possible with systematic records.

Insurance and legal documentation: Quarantine records with dates, treatments, and health assessments at discharge are the documentation that supports insurance claims and dealer liability positions.

Quarantine certificates: For dealers and hobbyists who want to document fish health for buyers, the quarantine record is the source document for the certificate.

What to Record

In KoiQuanta, record at each quarantine entry:

Fish details (variety, size, source, purchase date)
Parameter readings with dates
Treatment events (product, dose, date, reason)
Daily observations (behaviour, feeding response, any signs)
Any disease events, including investigation and treatment
Discharge date and health status at discharge

For batch quarantine (multiple fish from the same source), batch-level records are acceptable for shared observations. Individual fish records are needed when a specific fish deviates from the batch.

Part 6: Discharge Criteria and Transfer

The Discharge Decision

The discharge decision is not based solely on elapsed time. A fish that has completed 6 weeks in quarantine has met the time requirement. It still must meet all discharge criteria:

No disease signs for a minimum of 7 days before proposed discharge date
Normal feeding response for at least 3-5 days
Normal behaviour
All scheduled treatment steps completed
Water quality stable and within normal range throughout the final observation week

In KoiQuanta, the discharge checklist must be confirmed before the quarantine record can be closed. This prevents the most common quarantine failure - premature discharge.

The Transfer Process

With discharge criteria confirmed:

Confirm temperature within 2°C between quarantine tank and display pond
Adjust temperature gradually if needed (never shock transfer)
Net gently, minimise air exposure
Float transfer container in display pond for 15-20 minutes
Release and observe

Post-transfer: elevate observation frequency for 2-3 weeks. Watch for disease signs in both the new fish and the existing collection.

Part 7: KoiQuanta in the Quarantine Workflow

KoiQuanta manages every component described in this guide:

Protocol scheduling: Day-by-day reminders for treatment doses, parameter tests, and observation windows
Parameter logging: With trend analysis and alert thresholds
Observation recording: Structured daily logs with sign-specific fields
Disease event tracking: Linked to the quarantine record and fish profile
Discharge criteria checklist: Must pass before quarantine can be closed
Quarantine certificates: PDF export of the complete quarantine record
Analytics: Disease rates by supplier, season, and protocol - visible after 3-6 months of data

No other platform provides this complete workflow in a single koi-specific system. The new koi quarantine protocol details the standard 6-week protocol. The koi quarantine hub connects all quarantine-related resources.

Frequently Asked Questions

What is the most complete koi quarantine guide?

A complete koi quarantine guide covers all six components: quarantine setup (tank, filtration, equipment, medications), the arrival protocol (acclimation, initial observation), the standard protocol schedule (observation, treatment timing, parameter testing frequency), disease event management during quarantine, record keeping practices, and discharge criteria before transfer to the display pond. Most quarantine resources cover setup and a basic protocol but don't address disease event management within quarantine, systematic record keeping, or discharge criteria in detail. This guide and the KoiQuanta platform address all six components as an integrated system.

What does a proper koi quarantine involve?

Proper koi quarantine involves a minimum 6-week isolation period in a correctly sized, cycled quarantine tank with its own dedicated equipment. It includes prophylactic praziquantel treatment at days 7 and 21, salt at 0.3% for osmoregulatory support, daily observation with logged results, parameter testing at appropriate frequency (ammonia daily, pH twice weekly, KH weekly), a defined disease event response protocol, and discharge criteria that must be met before transfer. It's not just a waiting period - it's an active management period with scheduled interventions and daily monitoring. The quarantine record, including all observations, parameter readings, and treatment events, is the evidence that the protocol was followed correctly.

What software helps manage koi quarantine?

KoiQuanta is the only purpose-built koi quarantine management software. It provides day-by-day protocol scheduling with automated reminders for treatment doses and observation windows, structured daily observation logging, parameter tracking with trend analysis, disease event logging linked to quarantine records, discharge criteria checklists that must pass before quarantine can be closed, quarantine certificate generation for dealers and hobbyists, and analytics showing disease rates by supplier source and season. No other reviewed app has purpose-built quarantine management functionality at this level - alternatives are either generic parameter loggers or generic aquarium apps that address a fraction of the quarantine management workflow.

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Sources

Associated Koi Clubs of America (AKCA)
Koi Organisation International (KOI)
University of Florida IFAS Extension Aquaculture Program
Fish Vet Group
Water Quality Association