How to Keep Koi From Eating Pond Plants (8 Easy Tips)

In just about any aquatic ecosystem, plants are an essential component for healthy and natural functioning; and your pond is no exception. For example, most plants supply food and shelter to a plethora of organisms like macro and micro invertebrates (both of which provide food for your fish and other organisms), birds, mammals, and fish, all of which add to your pond’s biodiversity overall charisma. Research has found that the presence of native aquatic plants can facilitate many times the biodiversity than water bodies lacking vegetation.

Many plants also help soak up pollutants and excess nutrients, like fertilizers, nitrates, ammonium, and phosphorus, thereby acting as organic filters and preventing algae overgrowths or blooms, while also oxygenating the water.

Placing your plants in pots (clay, non-corrodible metal, or glass work best), shelves, or baskets and then putting them in your pond can prevent predation on the sensitive roots and lower stems of plants, allowing the plants to establish enough that they should be able to withstand a small amount of predation later on. You’ll only be able to do this with plants that don’t have extensive roots systems (although this is also a useful method for preventing cattail rhizomes from spreading out of control).

You can also create a different sort of natural shelf in your pond for emergent plants, where the substrate is only an inch or two below the waterline and then it abruptly drops off beyond the plants. Theoretically, this shelf will be too shallow for the koi to swim to (though some goldfish may be able to get to it), and the abruptness of the shelf itself, as opposed to a gradual depth change, can make it more difficult for them to get to the plants. As an added layer of protection, you can place rocks along the edges of the shelf to further deter fish from being able to swim onto it.

2) Choose Non-Palatable Plants

Just as people don’t find everything palatable (tasty), goldfish and koi are also a bit picky about which plants they like to eat. Goldfish, for example, don’t find anacharis, anubias, onion plant, hornwort, or waterweed to be tasty unless they’re quite hungry or have a nutrient deficiency (so make sure you’re feeding them a balanced diet!).

Among the plants that koi don’t find to be overly tasty are hornwort, eelgrass, horsetail, and lotus (though you’ll need to be sure to use species of this that are native to your region, as lotus and lilies can easily spread out of control).

3) Increase Feeding Frequency & Food Quality

Oftentimes, fish will browse on plants if they’re hungry or have nutrient deficiencies which they may be lacking in their normal diets. To combat this, feed your fish more regularly (but only as much as they’ll eat in a five-minute span), and be sure to feed them a high-quality diet that fulfills all of their nutritional needs.

If you’re already using a high-quality feed with all the right ingredients, you could try switching to a feed with higher wheatgerm content, as this should help keep them feeling fuller for longer. On top of pellet feeds, if you’d like to mix up your fish’s diet with more natural ingredients, you can also consider some homemade koi food recipes, as this can help keep their taste buds varied so they stop looking for extra food around the pond.

4) Use Koi Plant Protectors

Plant protectors come in a variety of forms. For aquatic plants, they’re typically mesh, almost bag-like, structures (except open at the top to allow the plant to grow), that are narrower at the bottom and weighted down somehow at the base.

These particular protectors, also called water lily koi protectors, are designed to protect floating species of plants. For submerged plants, you can simply place mesh netting around them, or fencing with holes too small to pass through (make sure that it’s non-rusting if you use metal). To protect roots, you can spread gravel across the bottom of your pond.

5) Separate the Tasty Plants

Though perhaps not ideal, if you’re really having trouble with your fish eating your plants or just want species that you know they’ll eat, you can divide up your pond. You can accomplish this with fencing, mesh, rocks, shelves (as talked about in the first point on this list), differing water depths, a natural bog filter (which typically consists of gravel and also acts to help purify your water), or a water liner.

You could also utilize entirely different ponds, one for fish and the other for aquatic plants, perhaps with terrestrial plants planted around the fish pond so you still have some vegetative aesthetic. With these methods, you can still have the plants that you desire but your fish will not be able to get to them.

6) Use Rapidly Growing Plants

Hygrophila polysperma (also known as dwarf hygro or Indian weed), water sprite, water wisteria (which is quite hardy to boot), anacharis, and hornwort are all rapidly growing plants.

7) Add Tough, Thick Leaved Plants

Predictably, plants with thick, tough leaves will be more difficult for fish to eat. Watershield has thick leaves that float atop the surface of the water, but the leaves, stems, and rhizomes also have a mucilaginous substance that makes them less palatable depending on the fish species. Sagittaria, a genus that includes arrowhead, also typically has quite thick leaves that aren’t easy to consume, but be aware that some species of sagittaria may be invasive in some areas.

8) Add Rocks & Gravel To Substrate

Koi in particular are known for digging into sediment both out of instinct and to get to any tender plant roots to nibble on. For plants that have tasty roots, you can protect them by placing gravel or rocks all over the bottom of your pond. You could also utilize a mesh covering, placed just underneath the existing substrate but above the roots.

This method may be an issue for species that need to have their roots or rhizomes cut back regularly to prevent overgrowth, such as cattails or water lilies, as you would have to move the rocks or mesh a couple of times a year to trim the plants so they don’t take over your pond.

What Are Other Benefits to Pond Plants?

Including plants in and around your pond also provides shade, thus aiding in naturally regulating your pond’s temperature so it’s more comfortable for its residents. Many birds and mammals will take advantage of any extra plant matter, like fallen leaves or dead plants that have floated to the surface, and utilize them to build nests and dens. Your fish will also be able to find cover from predators and heat amongst the plants, while also giving them a safe place to lay their eggs. In addition, plant roots will help prevent erosion and keep your substrate in place, thereby keeping your water clean and clear.

However, some commonly kept pond fish species like koi and goldfish really enjoy munching on a variety of pond vegetation. While some predation helps keep plants from growing out of control, too much can make it difficult to keep and maintain these plants. To help prevent over browsing, below we’ll discuss a few ways to deter your fish from chomping on your plants!