Asagi and Shusui koi swimming

With the varieties of koi that are available, it is conceivable that you will never build a pond big enough to get your fill of all the different types. But sometimes pond owners will look to add a little different spice to their ponds.

Koi are non-aggressive fish, and can live in harmony with other freshwater dwellers, some of which have added benefits like eating algae, detritus or undigested food.

Here are some factors to consider before deciding to add other species of fish to your koi pond:

Temperature — some pond mates might be able to handle the warmer waters of a tank, but won’t cut it in the rigors of icy water if your winters are cold.

Load — Koi already create a lot of natural waste, so you will also need to take into account how the new additions add to your filter load.

Size — some pond mates can grow to be quite large, and in some instances will eat the smaller cohabitating fish or their offspring.

Competition — to the victor (or the larger fish usually) go the spoils. Eating can become a competitive sport for some smaller pond dwellers.

Algae Eating Pond Mates

Chinese Hi Fin Banded Shark

Chinese Hi Fin Banded SharkWho doesn’t want a shark cruising the depths of their pond? These hardy, freshwater fish are great pond mates for your koi. Hailing from the chilly waters of the Yangtze river, the “shark” gets  its name from the large dorsal fin—not a fearsome array of teeth. It prefers the algae growing in your pond, not other fish—or fingers.

Given the right care and conditions, Banded Sharks can live for decades and grow to 3ft in length. Next Day Koi will periodically have Banded Sharks in stock, but as they are endangered, they will sell pretty quickly when available.

Trapdoor Snail

Trapdoor SnailThis tough snail is able to endure colder weather and has an appetite for algae. They will also eat all the dead stuff that other pond dwellers won’t or can’t. It has to be noted, however, that snails will only eat a very small amount of whatever is left over. Don’t expect them to be the ones that keep your pond in pristine condition.

Snails ordinarily make good hors d’oeuvres for koi, and as hardy as they are, this snail no exception. If your fish are smaller, you can add small snails, but if you want to be on the safe side it is recommended that the Trapdoor Snail be introduced to your pond when it is about the size of a ping pong ball.

Attractive Roomies


4” Black Moor GoldfishThese tank favorites are part of the same family as koi. They are much smaller, but like their cousins, they can generate a lot of waste. They are also a hardy pond denizen, but might not be as visible in deeper pools.

It is also good to know what you are getting as there are two different “classes.” Pond goldfish will be less expensive and less varied (think state fair prize). This “class” includes Comet, Sarasa Comet, Yellow Comet, Shubunkin and different varieties of Fantail.

The other class is Fancy Goldfish (or Imported Goldfish). They are typically imported from Asia, come in a much larger variety and will set you back quite a bit more than pond goldfish (and there are show quality goldfish whose cost can be very, very high). They include Oranda, Ranchu, Ryukin, Wakin, Moor, Butterfly Tail, Lionhead and Pearlscale.

Next Day Koi has a full and wide selection of goldfish for sale including Comets (usually the best variety to add to an outdoor pond), Shubunkins, Moors, Wakins and Fantails.

Golden Orfe

Golden OrfeAlso known as an Ide, as its name suggests it is an orange-gold mix (although it can be yellow or pinkish). Orfe were popular before koi came into prominence and are capable of sharing the pond with koi. They work better in smaller groups and will usually stick together.

They will eat insects, snails and worms, as well as smaller fish, so if you are looking to breed your koi it is worth noting that Orfe will eat fry. And vice versa. Although they can grow up to 20 inches, Koi will help themselves to smaller Orfe.

Bottom Feeders

Catfish and Barbel

Either of these types of bottom feeders can co-exist with koi and can be beneficial additions to larger koi ponds. Especially the Barbel, whose bottom-feeding diet can help to keep pond floors clear of all the stuff that the koi miss.

Catfish can grow to be large enough that they become a potential danger to your koi. They also have a tendency to stir up the sediment on the bottom, lowering visibility.

Golden Tench

This colorful bottom feeder aids filtration and helps to clear the debris on the pond floor. Its eating habit of light digging and sifting through the media on the pond’s bottom can help the filter system to pick up suspended waste and cycle it out.

Next Day Koi has a large selection of koi and goldfish for sale. Our interactive website allows our customers to filter their search according to type, color, size, price and breeder, thereby providing a truly customized experience.

Contact our friendly staff today to see how we can get a koi or goldfish into your pond or tank.

7 responses

    1. Hey Stan, We apologize, as we do not offer any Golden Tenches. We hope you understand. Perhaps, try checking around your local area to see if any pet shops or suppliers have them. Thank you.

  1. Anthony :

    Hi hope you can help
    I have recently started a pond and had it stocked with Japanese koi I have had already some koi in a tank which I believe now need a larger home but was told not to introduce them into my pond as they were Israeli koi is this a problem can I not mix them ?
    Any help would be much appreciated thanks

    1. Hello Anthony,

      The issue isn’t that the fish being from Israel would be harmful to add to your pond with your Japanese Koi, as much as you would want to take precautions when adding any fish, regardless of the source to your existing fish. Doing your best to stress the fish as little as possible and trying to properly acclimate them into the pond is key. Depending on their size, it may be challenging. Perhaps adding some pond salt to the water will reduce the stress on the pond fish and fish you will introducing.

      Thank you.

  2. I have a 500 Pond My fish keep dying I check the water and the Water is fine.I have koi fish hight fin stark 4 and two pond loach I don’t know what to do

    1. Hi Dino, Aside from checking water parameters to ensure that the readings are good for all fish you have in this pond, it sounds as though your pond may be technically overstocked. Just one Koi fish needs about 100-125 gallons of water for itself. If you add up all fish you have in your pond, the number of fish you have is likely too many and may be causing some water quality issues. Perhaps look at your stocking density and take a few of these fish out for better results.



    Hope this finds you well. I have a 45 gallon tank to around 50 gallon tank. I have three Koi in it. I was wondering what kind of plans and bottom feeders I can put in the tank? I know that plans will can be destroyed by the Koi so I wondered what is hardier plant to keep with Koi?



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