Can I Keep My Koi Fish Inside?

Updated on July 2, 2019
Jana Louise Smit profile image

Jana worked in animal welfare with abused and unwanted pets. She loves sharing her hands-on experience regarding domestic and wild critters.


What You'll Learn About Koi

  • When keeping koi indoors is the better option
  • The reason why it's often not a permanent solution
  • What equipment is needed
  • Planning and installation options
  • Safety precautions

Size and Seasons Matter

Ideally, koi should be kept outdoors. In large spaces, they grow to their full size and have unrestricted movement. Koi love a shoal—something that's not always feasible with an indoor setup. There are times when the latter is a solution. Koi stay inside when there's a problem with the pond, winter is harsh, one is sick, a new arrival is undergoing quarantine or when fish are small enough to live long-term inside an aquarium or indoors pond. The latter is also a good choice for koi-lovers who live in an area that prohibits the hobby outdoors.

Why It Cannot Always Be Permanent

Small fish make indoor koi keeping possible. Unfortunately, koi grow rapidly during their first years. Even when purchased as a baby, it will outgrow its tank in about a year. One can replace them with younger, smaller koi. The only problem is that keepers become attached to their fish since koi turn quite tame. If the indoor pond can only support growing koi for a year or two, this might lead to a heartbreaking decision to give them away. For this reason, most people who try indoor ponds either expand to the outdoors or stop altogether, since house koi also require more care.

Watch the Windows

Keep your indoor koi away from windows and rather supply them with full spectrum light beams.
Keep your indoor koi away from windows and rather supply them with full spectrum light beams. | Source

The Perks

Alright, it's not all doom and gloom. Here are perky reasons to consider an indoors environment.

  • You'll save in the winter. During colder weather, the utility bills connected to an outdoor pond can rise exponentially
  • In an aquarium, you can see your beauties clearly
  • It brings an exquisite touch to home décor
  • For housebound individuals, it can be very therapeutic to view the tranquil mix of water, movement and colour
  • The pond brings a slight humidity increase, which can lessen the chances of dry skin some people are prone to during the winter.

The Aquarium

The fish tank is a good choice for baby koi. However, it needs to be large (up to 200 gallons). You can keep a couple of fish together, but don't consider this option if you aren't willing to give away your pets after about a year when they outgrow their aquarium. Though time is an issue, the aquarium is a fantastic way to temporarily house your koi while installing a bigger and better indoor pond.

Equipment for the Pond

Koi can be an expensive hobby and when it comes to keeping them indoors, the more pricey the equipment, the safer they are. Don't risk cheap products with this project.

To build your pond, you'll need the following:

  • A drain line that can be installed at the bottom or next to the pond
  • The best filter you can buy. Consider getting only a bead or three-chambered filter. Purchase with caution—some products promise the heavens but cannot handle the mess your koi are guaranteed to make. If a filter looks skimpy, don't buy it
  • Water pump
  • Air pump and stone
  • Full spectrum fluorescent bulbs and reflectors.

Make It Beautiful

The beauty of a koi pond is enhanced when you add suitable plants and even statues.
The beauty of a koi pond is enhanced when you add suitable plants and even statues. | Source

Setting up the Pond

This stage needs careful planning and understanding. Proper installation could prevent many headaches and repairs in the long run. Talk to koi keepers who'd done this before, discuss it with professional builders if you don't want to do the installation. However, if this is a personal project you'd enjoy doing yourself, then make sure you are a hundred percent clear on what needs to be done.

Here are the basics of what you can expect:

  1. A proper location capable of accommodating the pond's weight and proportions, which must have a minimum depth of 4 feet
  2. Waterproofing the room
  3. Different options such as the preformed pond or a timber structure with a liner
  4. Correctly adding all the equipment and plumbing
  5. A settling period to condition the water; usually done by adding goldfish for the first few weeks.

Safety Precautions

Setting up your indoor koi pond sounds like a lot of work! In actual fact, it's not hard —once you grasp the essentials, the equipment and tools. Learn all you can about the setup process, the costs involved and how to complete the project safely.

Here are just a few tips to consider:

  • If your aquarium was just a temporary home and the fish are about to be moved to the pond, never reuse the equipment from your aquarium in the pond
  • Don't ignore small leaks on the floor next to the pond; investigate and seal as soon as possible
  • Take steps to safeguard children and pets around your pond
  • Keep a tight reign on water quality—the chemistry of an indoor pond is more prone to imbalances
  • Don't overpopulate the pond
  • Consider investing in flood insurance.

Questions & Answers

    © 2018 Jana Louise Smit


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