Moving Koi from Quarantine to Display Pond: Protocol

By KoiQuanta Editorial Team|Updated Mar 2026

A koi that passes all discharge criteria has less than 2% risk of introducing disease-after-pond-treatment) to the display pond. The discharge criteria process is what separates successful quarantine from quarantine that simply delays the inevitable. A fish transferred before it meets all criteria carries the same disease risk as an unquarantined fish - the quarantine time was spent but the benefit wasn't achieved.

KoiQuanta's discharge checklist must pass before transfer is logged and quarantine closed. No competitor manages the quarantine discharge and transfer as a formal protocol step.

TL;DR

If a fish showed flashing on day 28 and showed no signs after treatment from day 30 onwards, it needs a clean 7-day period from day 30, pushing the earliest possible discharge to day 37 minimum.
Normal feeding response** The fish is eating well - actively taking food at normal quantities - for at least 3-5 days before discharge.
If the standard protocol calls for praziquantel at days 7 and 21, both doses were given on schedule.
If they differ by more than 2°C, adjust gradually over 30-60 minutes before transfer.
Don't transfer a fish from 18°C quarantine water directly to a 25°C display pond.
If you reach 3 weeks with no issues in either the new fish or the existing collection, the transfer was successful.
A fish that needs an extra 2 weeks in quarantine before meeting discharge criteria costs 2 weeks of quarantine tank space.

What Are Discharge Criteria?

Discharge criteria are a defined set of conditions a fish must meet before it can safely leave quarantine. They're the objective standards that determine whether quarantine was successful, not just whether the scheduled time elapsed.

A fish can go through a full 6-week quarantine period and still fail discharge criteria if:

It's still receiving active treatment for a disease event that occurred during quarantine
It showed signs of illness in the final week of quarantine that haven't fully resolved
Water quality in quarantine deteriorated and the fish hasn't been observed under stable conditions for the full observation period
A treatment dose was missed partway through quarantine, potentially leaving the fish with partial treatment that didn't fully resolve the issue

Time in quarantine is necessary but not sufficient. The criteria are the sufficient condition.

The Standard Discharge Criteria

Before transferring any fish from quarantine to your display pond, confirm all of the following:

1. Minimum quarantine duration met

The fish has been in quarantine for the full required period - typically 4-6 weeks for standard quarantine, with extensions for high-risk situations (KHV risk, disease events during quarantine, uncertain source).

The clock starts when the fish enters quarantine, not when it arrives at your facility if there was a delay between arrival and quarantine tank entry.

2. No disease signs for the final 7-10 days

The fish has shown no disease signs - no flashing, no clamped fins, no lesions, no abnormal behaviour, no reduced appetite - for at least 7 days before the proposed discharge date.

This criterion catches fish that appear to recover from a disease event during quarantine but still have residual infection. If a fish showed flashing on day 28 and showed no signs after treatment from day 30 onwards, it needs a clean 7-day period from day 30, pushing the earliest possible discharge to day 37 minimum.

3. Normal feeding response

The fish is eating well - actively taking food at normal quantities - for at least 3-5 days before discharge. A fish with reduced appetite in the final days of quarantine is showing a stress or health sign that warrants investigation before transfer.

4. Normal behaviour

The fish is behaving normally: swimming actively, positioned in normal areas of the tank, not isolating, not hanging at the surface, not showing any abnormal posture. Behavioural abnormalities in the final days are a warning sign.

5. All scheduled treatments completed

Every treatment step in the protocol has been completed. If the standard protocol calls for praziquantel at days 7 and 21, both doses were given on schedule. If any treatment step was missed (or delayed significantly), the protocol should be considered incomplete even if the full time period has elapsed.

6. Water quality stable and within normal range

The fish completed the final week of quarantine in stable, normal koi pond water quality tracker - not in recovering water after a parameter event, not in elevated ammonia or nitrite. Water quality during the final observation period must be representative of the conditions the fish will experience in the display pond.

How to Perform the Transfer

Once all discharge criteria are confirmed:

Step 1: Temperature check

Measure the quarantine tank temperature and the display pond temperature. They should be within 2°C of each other. If they differ by more than 2°C, adjust gradually over 30-60 minutes before transfer. Don't transfer a fish from 18°C quarantine water directly to a 25°C display pond.

Step 2: Prepare transfer equipment

Use a clean, appropriate transport container - a bag with water from the quarantine tank, or a transport bowl. Don't use equipment that contacted diseased fish without thorough disinfection.

Step 3: Net gently

Net the fish with an appropriate soft net. Minimise air exposure. Transfer promptly.

Step 4: Acclimate

Float the transfer bag or container in the display pond for 15-20 minutes to equilibrate temperature and reduce transfer shock.

Step 5: Release and observe

Release the fish into the display pond. Observe for the first 30-60 minutes. Initial exploration behaviour is normal. Fish hanging at the surface or retreating to corners for extended periods suggests stress.

Post-Transfer Monitoring

For 2-3 weeks after introducing a fish from quarantine, maintain elevated observation frequency for both the new fish and the existing collection. Watch specifically for:

The new fish integrating normally (eating well, swimming actively, no signs)
The existing collection showing any new signs that might indicate disease transfer

The 2-3 week post-transfer period is the window when any disease that might have crossed over would be most likely to become visible. If you reach 3 weeks with no issues in either the new fish or the existing collection, the transfer was successful.

Log the discharge date, the passing of all discharge criteria, and the transfer event in KoiQuanta. The quarantine record is then closed with a successful completion status. This record becomes part of the fish's permanent health history.

When to Extend Quarantine

Quarantine should be extended beyond the standard period when:

A disease event occurred during quarantine and hasn't been fully resolved
Discharge criteria haven't been met at the standard endpoint
The fish came from a KHV-risk source and you're using temperature-based KHV challenge protocol
The fish showed abnormal behaviour that's resolved but you want a longer clear period to build confidence

Extension is the correct decision in these situations. A fish that needs an extra 2 weeks in quarantine before meeting discharge criteria costs 2 weeks of quarantine tank space. The alternative is introducing a potentially infected fish to your display pond, which costs the disease event that follows.

The koi quarantine discharge criteria guide covers the specific criteria in more detail. The new koi quarantine protocol covers the full standard quarantine process.

Frequently Asked Questions

How do I safely move koi from quarantine to my main pond?

Confirm all discharge criteria are met: minimum quarantine duration elapsed, no disease signs for at least 7 days, normal feeding and behaviour for 3-5 days, all protocol treatments completed, and stable water quality during the final observation week. Check that quarantine tank and display pond temperatures are within 2°C, adjusting gradually if not. Net gently, minimise air exposure, float the transfer container in the display pond for 15-20 minutes to equilibrate temperature, then release. Observe for 30-60 minutes after release. Monitor both the new fish and the existing collection with elevated frequency for 2-3 weeks post-transfer.

What checks do I do before transferring koi to the display pond?

Run through the discharge criteria checklist: Has the fish completed the minimum quarantine duration? Has it been sign-free for the final 7-10 days? Is it eating normally? Is it behaving normally? Were all scheduled treatments administered? Is water quality stable and within normal range? All criteria must be met - not just elapsed time. A fish that meets time criteria but hasn't been clean for 7 days, or that missed a treatment step, has not successfully completed quarantine. In KoiQuanta, the discharge checklist must pass before the quarantine record can be closed, preventing premature transfer by default.

Should I acclimate koi temperature before transfer?

Yes. Temperature differences above 2°C between the quarantine tank and display pond cause temperature shock stress, which can suppress immune function in fish that may already be mildly stressed from the transfer process. Check temperatures before transfer. If they differ by more than 2°C, place the fish in a transfer container with quarantine tank water and float it in the display pond for 15-20 minutes before release. For larger differences, a gradual adjustment over 30-60 minutes is better than a direct float. Temperature matching is straightforward and eliminates one of the avoidable stress factors at transfer.

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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