Koi Care, how to Quarantine Koi

Many beautiful collections of koi are lost every year
because pond keepers do not quarantine their new koi fish.

One of the major causes of koi deaths and sickness this year and every year is the failure of pond keepers to quarantine their new koi. Collections of koi that were family pets for years, to a collection of hand-picked Japanese show koi worth over $150,000.00, all gone, because new koi with health problems were introduced to their pond.

Let’s make sure this catastrophe does not happen to you. But first, before we talk about koi quarantine and if you have a nice clean pond full of happy, healthy koi that you have become attached to over the years. Ask yourself this question: “Am I willing to risk the health of my koi and pond for a new koi fish?”

Now there are times when adding new koi to your koi pond is necessary and that’s when knowing how to properly quarantine new koi is priceless because it greatly reduces the risk of introducing koi parasites and bacterial infections to your koi pond.

Here’s how to setup a Koi pond fish Quarantine Tank

Koi Quarantine Tank type and size:

Koi Quarantine Tank Type:

One of the best tanks you can buy to quarantine your new koi is made by Rubbermaid®. Their tanks are made for watering livestock and are very strong but light and priced right. Plus, they have a bottom drain that you can attach a valve to that makes them very easy to clean and do water changes.
Another good feature is they are deep which will help keep your koi from trying to jump out.

There are portable tanks on the market used for showing koi however; unless you are keeping the tank inside I don’t think they would be strong enough to protect your koi from raccoons and other wild critters.

Quarantine Koi Tank Size:
You do not want to crowd your koi when they are in quarantine.

One of the best quarantine sizes for the Rubbermaid® tanks are 150 gallon and the 300 gallon. With proper care, lots of water changes and testing the water every day in your koi quarantine tank for ammonia, nitrites and pH, a 150 gallon tank should handle up to four or five 10 inch koi.

Location of your Koi Quarantine Tank:

The location of your quarantine tank should be near an electrical outlet, a fresh water source and not in direct sunlight all day.

Note: You should be able to buy a Rubbermaid® tank in most animal feed stores. If you can+not find one, there is a Rubbermaid® outlet located in Wooster, Ohio that will give the name of a Dealer in your area that stocks their tanks.

Koi Quarantine Tank covers, Heaters and Aeration:

Koi Quarantine Tank covers:

All quarantine tanks must be covered to protect your koi from jumping out and to protect your koi from predators. However, your koi do need sunlight and open air.

Do not use glass or clear plastic because it will increase the water temperature. A strong, heavy plastic mesh with a strong frame should work as long as it is predator proof.

Important: A floating cover ON the surface of the water: Koi can be scared very easily, causing stress, especially new koi. In order to reduce stress, which can cause a weaken immune system; float a piece of Styrofoam on the surface of the water for the koi to hide under. Plus, it also makes a good place for your koi to take cover from the sun.

Koi Quarantine Tank Heaters:

Koi quarantine tanks should be kept at a temperature of 74° to 78°. Higher temperatures increase parasite and bacterial growth and the warmer water contains much less oxygen. At Lower temperatures, the treatments used in the quarantine koi tank are not as effective.

Quarantine Koi Tank Aeration:

Lots of aeration with tiny bubbles coming from the bottom of the quarantine koi tank is very important.

What is the #1 problem pond keepers’ neglect when using their Quarantine Tank?


You can have the very best of everything for your quarantine tank, however, if you do not keep the water in 100% condition, free from waste, ammonia, nitrites, low nitrates and low pH your fish will suffer. You must place an “aged” filter on your quarantine tank as soon as you introduce your new koi.

An “aged” filter is a filter that has the “good bacteria” already started in the filter. If your filter is not “aged” the water in your quarantine tank will quickly become toxic with ammonia. Many times pond keepers think their koi are sick from a parasite or bacterial problem only to find poor water quality in their quarantine tank is really the problem.

A FAQ: How do I maintain an “aged” filter so it’s ready for my quarantine tank?

There are a few of ways to make sure your quarantine koi tank has an “aged” filter.

1- If you’re going to be buying a number of new koi over a long period of time (*NOT Recommended*) you can set up a permanent quarantine koi tank with a filter.

However, you must keep at least one or two fish in the quarantine koi tank at all times so they can produce the ammonia your filter needs to keep the “good bacteria” alive from one batch of new koi to another. Some pond keepers will keep a couple of inexpensive comets in their quarantine koi tank at all times.

The biggest problem with this set up is you’re maintaining another “pond” and it’s much more work.

2- Have two filters that use the same “filter padding”, place one filter on your pond and the other on your quarantine koi tank. When you buy new koi, take one “aged” filter pad from the filter on your pond and place it in the filter on the quarantine koi tank, “instant aged” filter for your quarantine koi tank.

When you’re done with the quarantine, throw the filter padding out.

NEVER, NEVER, return the filter padding you used in your quarantine filter, back to your pond filter. Add a NEW filter pad to the filter on your pond. It will take two to three weeks before the new pad is really aged enough to add to the next quarantine koi tank filter. When you’re not using your quarantine koi tank shut it down.

3- Buy four sets of extra-large sponge filters that aquarium hobbyist use. A sponge filter works with air. Place two of these in your pond with sponges to age.

Place the other two in your quarantine koi tank with no sponges. When you buy new koi, take one or both of the “aged” sponges from your pond and place it in your quarantine tank, “instant aged filter” for your quarantine koi tank.

NEVER, NEVER, return the sponges you use on your quarantine tank, to your pond. Replace the sponges in your pond with NEW sponges.

Note The “sponge filters” do an excellent job of growing the “good bacteria” you need to keep the ammonia down in your quarantine koi tank, however, sponge filters do not do a good job of filtering the heavy waste. You’ll need another filter or you must vacuum the bottom of your quarantine koi tank to remove the heavy waste (sludge).

A FAQ: Now that I set up my quarantine tank how do I treat my new koi?

Here are the treatments you’ll need to really “clean up” your new koi in quarantine.

1. Treat for the number one parasite that causes many koi health problems, Flukes with a safe and gentle treatment: Aqua Prazi, two treatments 3 days apart.

2. Treat for any bacterial infections with Medi-Koi for 10 to 14 days.

3. Check your new koi for fish lice and anchor worm. These parasites are not microscopic and can be seen with naked eye.

4. If your new koi are Flashing after you treat them with Aqua Prazi then treat them with Terminate for other microscopic parasites. If you have any doubt, treat with Terminate.

Just by following these easy steps, your new koi will be safe to place in your pond with your other koi.

Need help, I’m here.
Thanks for your time,

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