Why Is the Water Turning Brown in My Koi Pond?

Crystal-clear water is a goal all koi pond keepers share, and it isn’t necessarily the most ideal. The natural habitats of Asian grass carp, the cold water species koi derive from, don’t generally feature clear water. Their primary ecosystems are rice paddies where the water tends to be muddy. The color of pond water doesn’t always reflect the health of the aquatic ecosystem. For example, murky green water that resembles split-pea soup is sometimes an indication that a natural pond is teeming with a nice balance of plants, fish, and other species. When the water in your garden pond turns brown, there are a few reasons that could explain this coloration, which isn’t always a harmful situation.

Organic Sedimentation at the Bottom

If you notice pond water turning brown during the summer, there’s a good chance the koi have stirred up the bottom because that’s where they tend to stay whenever temperatures are higher. This will happen even if the substrate of the pond is mostly rocks instead of dirt, and it means organic matter such as fish waste hasn’t fully decomposed and is forming a sediment layer. In massive ponds or lakes, a sturgeon fish can take care of this. In smaller ponds, a few crayfish will do, but we’ll mention two other methods below.

Terrestrial Plant Debris

When pond water turns the color of tea, it’s usually because it has actually brewed into a concoction of decaying plant matter. The aquatic plants in your pond aren’t to blame for this coloration, which is caused by fallen tree leaves and pine needles. Although your most essential koi pond supplies, such as the pond aeration and filtration system, are supposed to take care of this, the movement of the water column may not be sufficient, and you may want to look into installing a fountain in addition to the water pump. Adding liquid bacteria is also an excellent way to reduce organic plant debris.

How to Differentiate Between Organic Sedimentation and Plant Decay

To select the right method for clearing up pond water, you’ll need to determine what’s causing the water to turn brown. To do this, simply dip a glass container to scoop out some water from the pond, then allow it to rest for 24 hours and take a good look at its state. If it’s still brown, plant decay is the problem. If it has cleared up, you may notice a thin layer of organic sediment at the bottom of the glass or jar.

Clearing Up Brown Pond Water

In many cases, skimming the substrate, cleaning out filters, and changing 25 percent of the pond water will clear things up. Once you know tannins released by plant decay are the source of coloration, you can drop a bag of activated carbon into the pond. If organic sedimentation is the problem, keep an eye on the ammonia levels, add more bottled bacteria, get more plants, and make sure the biological filter is still in good condition.

It’s important to make sure you maintain good water quality to keep your fish healthy. To accomplish this, you’ll need koi pond filters, beneficial bacteria, pond vacuums, and several other supplies, all of which can be found at Aquatic Warehouse. Stop by our store located in Kearny Mesa, order what you need from our website, or give us a call with any questions you might have at 858-467-9297.