how to: Make an indoor koi tank

Housing fish indoors is a great way to ensure your fishes safety as well as being able to grow and enjoy them on a year round basis

Of course, because koi are so big, a large tank is required to house the fish properly. These tanks can weigh a lot, so need to be built properly if they are to hold water in the long run
I made this 4 x 8 tank with corner pins so it could be dissasembled

new tank syndrome

To avoid new tank syndrome, New tanks are immature biologically so ammonia and nitrite spikes occur until the beneficial bacteria levels build up. This can take 2 months or more systems should be started up at least 2 months before you plan to bring your fish in for the Winter. You start the cycling by introducing just a couple of small fish. A tank will not cycle without a source of ammonia, so you need to introduce it either with fish or with ammonia chloride for example.

One great technique to employ is having a smaller bead filter. You can move it in and out, and if done quickly, maintain the bio bed in the filter. In this case, fish and filter can be moved in at the same time with usually a minimal hiccup in water quality. One quickly learns in this hobby that a mature filter is worth its weight in gold

See a video of this tank in action on our Filtration page [kaldnes filter]

Koi Tank Construction Tips

  • Put a layer of 1"+ styroboard on the bottom of the tank. This will keep it off the floor, insulate, and help balance the weight
  • The tank must be structural sound because of the heavy mass of water. I wrapped 3 rings of 4"X4" 's around the circumference of the tank pictured above. If you can get it against a wall or in a corner, all the better
  • Corners should be filled with construction adhesive first before applying liquid rubber
  • Don't forget to incorporate filter feeds, aeration ports and drains
  • Several coats of liquid rubber should be applied. Re-application can occur in less than 12 hrs. - it dries better when it is warmer

Kens Indoor Koi Tank

Ken who works in our shop has a great indoor tank of about 2K gallons. He moves his fish in and out seasonally and as a result of this extra care, has had some of his fish for over 20 years

Large 8 x 16 Indoor Koi Tank Video