As the world becomes more globalized, we’re seeing worlds combine in new and unique ways. One of the results of globalization is a larger variety of aquatic plants and animals available to the aquarium trade. Now your options for unique and beautiful koi ponds are greater than ever. However, along with all the great options for your aquarium or pond come unwelcome invasive species. You’re probably familiar with the idea of invasive species.

You’re probably familiar with the idea of invasive species, like the Snakehead fish. The Snakehead fish is predatory and able to move short distances over land. It has populated New England all the way from Asia. Another invasive species you may have heard about are Japanese beetles, these critters will destroy your rose bushes and gardens. Snakeheads were brought as food stock, and the Japanese beetles were accidentally introduced to the US.

Animals are not the only kind of invasive species, however. Aquatic plants, when brought to lands they didn’t originally come from can cause rampant destruction in new rivers, lakes, and oceans. These are the three most common invasive plants you may come across in the aquarium trade. Once you’ve learned about the kind of damage they can create, you’ll learn how to prevent it.

Water Lettuce

Don’t let the name fool you. While it’s got the least threatening name possible, this plant can cause massive damage. It has invaded Hawaii and can cause problems with rice and taro crops. This plant floats, and can clog up rivers and lakes while out competing the native plants. Additionally, Water Lettuce lowers oxygen concentration, creates mosquito nurseries, and steals habitats from other plants and animals.

One of the bigger challenges for managing Water Lettuce is the fact that it’s inedible. Water Lettuce is full of calcium oxalate crystals which can cause burning in your throat and mouth, and damage your GI tract. Because of this, many animals will not eat Water Lettuce. In fact, only two animals are good at eating Water Lettuce. The hippo and the manatee are happy to munch down on Water Lettuce, however there’s no effective way to use these animals to fight the invasion.  To make thinks worse, Water Lettuce is ugly on top of all its other qualities.

Water Hyacinth

The Water Hyacinth is beautiful, and you may be tempted to use it as an ornamental plant in your koi ponds. However, you shouldn’t use hyacinth in any kind of pond, whether it’s a koi pond or otherwise. Water Hyacinth grows very tight, and can quickly grow in massive patches, acres wide. Once Water Hyacinth begins to grow like this it blocks light from reaching the lower levels of the water. This does more than stop other plants from growing. When the light can’t reach under the water hyacinth it stops lower plants from photosynthesizing, and your koi pond can stop producing oxygen.

On top of the decreased oxygen production, the mere presence of the Water Hyacinths stops gas exchange. If you let your pond get overgrown with water hyacinth you’ll end up with an oxygen starved pond filled with dead or dying fish. Because water hyacinth grows so thick, it slows or stops the movement of water on the surface of the pond. This will cause rapid algae growth as well as breed mosquitos.

Water Hyacinth grows and reproduces in two ways. The first way is through budding. While in their active growing season, the water Hyacinths grow smaller plants, or “daughter plants” that are essentially small hyacinths growing off the parent plant.  Once the daughter plant has grown and established enough, it will break off and start the process over on its own. In addition to the budding method, hyacinths will reproduce by producing seeds. These seeds are especially sneaky because they can lie dormant for years waiting for the environment to encourage growth.


One of the features these plants have in common is how easy they are to care for. Of the plants on this list, the Anacharis is the easiest. The Anacharis only requires medium light, which is perfect for lakes or koi ponds. Additionally, it does not need to be planted to grow, and even thrive. When the Anacharis is floating, it will grow roots down the stem and draw nutrients directly from the water. It’s difficult to remove because it’s easy to create new ones simply by breaking the stems. Any pieces you leave behind when you’re removing them will immediately begin to regrow and start over.

Anacharis blocks out light and steals the nutrients of most native aquatic plants. Because Anacharis grows faster than these native plants it makes it easy for them to out compete the native plants. In addition, when left to grow freely, Anacharis forms thick mats of floating plant that make it difficult for recreational activities such as fishing, rowing, swimming, and even boating. If your propeller gets tangled in a mat of Anacharis, your day is surely ruined.

How to Prevent These Plants from Growing in Koi Ponds

The most effective way to keep these plants from being a problem for your koi ponds is to avoid them from the start. There are lots of species to choose from when starting koi ponds that you’ll always be able to find a safer alternative.

Look for plants that won’t survive in the wild where you live. However, if you really can’t find an alternative, or if you just love one of these invasive plants there are steps you can take to be safe. For starters, never release anything from your koi pond into the wild. You shouldn’t dump your pond’s plants into a stream, river, or another pond.

When you’re disposing of your plants, do so safely. You’re either going to want to dry them out completely, or freeze them. Whichever method you use, you should dispose of them in a sealed bag. Build stone walls around your koi pond to keep your plants separated from local waters in the event of a flood that could otherwise enable your plants and animals to escape.

Armed with this information you’re ready to build the koi pond of your dreams that’s safe for the environment. Aquatech Aquarium Service has a wide variety of supplies and equipment to help you realize your vision.