Protecting Plants in the Pond from Koi

by Elmer Epistola

Posted: September 1, 2004

Finding beautiful Nymphaea lotus plants in Manila is not easy, which is why I still remember the day I was able to buy one for only 500 pesos.  It was a very healthy plant, having clusters of large leaves around a huge base of roots.  More importantly, it had a bud that I knew would eventually become a majestic floral centerpiece in our pond very soon.  

True enough, the bud eventually bloomed into an elegant flower, which stayed at the center of our pond for weeks.  Then the unexpected happened.  The plant started to deteriorate quickly, losing its leaves one by one at a very alarming rate.  Before long, all that it had are small sprouts of leaves that are too small to be appreciated by the naked eye.  

Needless to say, I tried to determine what went wrong.  Upon closer inspection of the plant, I discovered that it no longer had any roots left.  I then realized that the koi made the roots a part of their daily buffet.  That explained why the koi loved tugging at the plant - they were eating it!   After that incident, no more plants in the pond for me.

Figure 1.  Koi love foraging on vegetation

Indeed, many koi experts  warn people about the incompatibility of plants and koi in the pond.  In fact, serious koi hobbyists (the purists) never put any plants in their ponds.  Whatever flora they need are simply used to outline the pond and accentuate it at highlight points.  

Then again, there are also koi enthusiasts who simply can't imagine a koi pond without plants.  To them, a koi pond with just water and fish is bare to the point of being 'unnatural.'  Furthermore, studies have clearly established that various plants have direct beneficial effects on the pond. 

Plants provide shade and security to koi.  They can also help stabilize the water temperature.  Plants also compete with algae in consuming nitrates in the pond, thereby helping to keep the water clear.  Lastly, and most importantly (to me, at least), plants add natural beauty and elegance to the pond if properly set up. This is why koi/plant hobbyists devise ways and means of protecting the plants in the pond from koi.

There are several ways by which koi can damage plants.  They can munch on them to their fill, as what has happened to our lily.  Being natural diggers, koi can likewise uproot them.  Koi also love using plants as breeding material, and can easily mess up your plant set-up doing so.

Figure 2.  Koi can easily detach leaves

from a plant

The natural thing to do to protect your plants, therefore, is to keep the koi away from them!  This doesn't necessarily mean that the plants will have to stay out of the pond.  One simply has to fence the plants in with barriers to keep out the koi. 

To protect the roots of the plant from koi, plant them inside a suitable aquatic planter or tub.  Choose a tub that has extra space for roots to grow in.  Pack the roots of the plant in the tub with loam or aquatic soil, before topping it off with a half-inch layer of gravel.  You can then submerge the tub in the pond, with the roots of your plant now properly protected.

To protect the stems and leaves of the plant, one can make a cylindrical fence out of plastic wire mesh.  This 'cylinder' mesh must start at the tub and end above the water line, in effect shielding the plant from the fish.  If properly set up, this fence would be hardly visible at all. 

A word of caution though - an improperly constructed fence can hurt your koi so make sure that nothing in your design can possibly be harmful to them.  Sharp edges or protrusions can easily damage a koi's skin, so nothing of this sort must be present in your fence.  Note as well that koi are good jumpers, so make sure that they will not be able to jump into your fence and get hurt or trapped in the process.

If what you have or want to have are water lilies, you can also protect them by constructing a 'floating' fence around them.  The floating fence will also use plastic wire mesh to protect the roots and leaves of your lilies, but this time they simply need to be supported by a floating frame.  Needless to say, the mesh will be underwater below the roots of the lilies to keep the koi out.

There are really many ways to keep your koi and plants in one pond, if this is what you prefer. On the other hand, the availability of these solutions doesn't mean that koi ponds must have plants.  After all, there are many koi enthusiasts out there who prefer not to have anything else in the water other than their highly-prized nishikigoi.  As I always say, it's really all up to each of us.