Every Koi carp enthusiast knows that if they want to keep their fish healthy they need to quarantine new fish.  Adding new fish to a pond can present you with many issues, but with careful water management it does not have to be stressful for you or your fish!

Essential Quarantine Equipment

  • UV Unit
  • Heater
  • Dechlorinator
  • Waterproof gloves
  • Nets
  • Bowls
  • Treatment mat
  • Anaesthetic
  • Parasite treatments
  • Wound-healing kit
  • Microscope
  • Koi health book

Water requirements

dechlorinatorTap water should, ideally, always be passed through a dechlorinator before it goes into a pond that holds fish since tap water can contain high levels of chlorine or other chemicals which can harm the fish or filter.

The ideal water-quality parameters would be undetectable ammonia and nitrite levels (below 0.05 when using a digital meter), nitrate levels of less than 10ppm, with PH in the region of between 7.5 and 8. These parameters would be ideal in any pond too. This excellent guide provides more information on how to dechlorinate tap water for your pond.

Temperature ramping

Once your new fish have been introduced to your quarantine system you should take a skin scrape to identify if any external parasites are present – if you find any then treat accordingly. The temperature of the quarantine system should be roughly the same as the temperature that the purchased fish were kept in.

As soon as the fish have been introduced into the quarantine system, the temperature should be raised to (or lowered to) and held at 15-16°C for 24 hours and then raised to a minimum of 23°C (maximum 27°C) over the next three days and held there for three weeks. The temperature should then be dropped back down to 15-16’C for another 24 hours and then raised back up to the same temperature as before (23-27°C) and held there for another two weeks. The intention with this process is to deliberately stress the fish in order to bring on an outbreak of KHV if the virus is dormant in any of your new fish.

Once the temperature has been raised, you can start feeding slowly, building up over a period of a week or two to allow the filtration system to adjust to the new stocking levels. During any temperature ramping, or after initial treatments, you should stop feeding for 24-48 hours and then introduce food slowly after this time. It is important to monitor the water parameters, too, particularly ammonia and nitrite levels.

Regular water changes are essential at a rate of a minimum of 10-15% per week. Ideally, the quarantine period should last a minimum of six-to-eight weeks and at least until you are entirely confident that the fish are happy and healthy. Temperature ramping should be done as a precaution but any other medications for external parasites should only be used if they are necessary. If you add new Koi when you’re quarantining existing Koi, you will have to start the whole process again, so it’s best to avoid doing this if you can.

Quarantine Timeline

Week 1

  • Carry out a skin scrape to identify if any external parasites are present and treat accordingly. Begin raising the temperature to 15-16C.

Week 2

  • Ramp the temperature up to 2-27C and hold it for three weeks.

Week 3

  • Observe the fish and treat if necessary.

Week 4

  • Observe the fish and treat if necessary.

Week 5

  • Bring the temperature back down to 15-15C for 24 hours and then take it back up again to 23-27C again for two weeks.

Week 6

  • Observe the fish and treat if necessary.

Week 7

  • Reduce the temperature of the quarantine facility to match the temperature of the pond that the fish will eventually be living in.
  • Check water parameters weekly – if in doubt, daily.

Final thoughts

monitor your fishBefore introducing quarantined Koi to your pond, make sure the water temperature in your quarantine system matches that of your pond. Also, test the water in both systems to make sure that they are the same. Once you have introduced new Koi to your pond you should monitor them on a daily basis, as you should do with any Koi as a matter of course.

After the quarantine period is over, and your new fish have been moved to your main pond, there should be no parasites within the quarantine system (whitespot, flukes and Trichodina can live in the filter without a host for short periods of time). If no bacterial or viral diseases have presented themselves then any naive fish can be left in the system to keep the filter, mature and running until you next require its services.

If you don’t intend to keep any fish in your quarantine system, you must drain it down completely and clean it. This avoids any build-up of ‘bad bacteria’ within the system that could infect any new fish once the system is started up again. Products such as Virasure-Koi and Virkon Aquatic are great for disinfecting nets and equipment and using them should ensure that no diseases present in your quarantine system are transferred elsewhere.