Is It Bad for Koi Ponds to Have Algae?

As one of the most ancient and resilient organisms on our planet, algae is something all koi pond owners should expect to find in their ponds. Paleontologists estimate that the most primitive forms of algae, which are microscopic, initially formed about two billion years ago. There are thousands of varietal algae species, and you can bet on dozens of them forming in your koi pond from time to time. It would be inaccurate to say algae is bad for koi ponds. Some types of algae are very beneficial in terms of promoting a healthy aquatic ecosystem, and you wouldn’t want to eliminate them. Other species such as phytoplanktonic algae actually promote adequate chemical oxygenation.

When Algae Becomes Problematic

A sign of excessive algae bloom in a koi pond is when water turns green and takes on the appearance of pea soup, but this is more of an aesthetic nuisance because it doesn’t let you see the fish below the surface. If the ammonia levels of your green pond water are close to zero and the koi are healthy, there’s no reason to panic. The problems begin when algae starts dying off and there’s no adequate aeration and biological filtration.

What Promotes Algae Bloom?

It would be biologically impossible to find a garden pond that’s completely devoid of algae. Remember—it’s not a swimming pool. You may not be able to see the fine green hairs, filaments, or dots, but you can bet that some algae life is present in a healthy koi pond ecosystem. The nutrients algae need to bloom will always be there—fish waste, bacteria, oxygen, and hydrogen are sufficient to cause algae to grow, but sunlight is the factor that completes the nutrition cycle. In sunny regions such as Southern California, pond keepers are more likely to end up dealing with algae bloom.

Getting Rid of Algae Bloom

Filamentous algae will float to the surface before it sinks to the bottom when it dies, which makes it easier to remove with a pond skimmer. You can pick up some algae detritus from the substrate with a toilet brush, but you should never use a scrubbing motion. It’s more important to focus on the dead algae at the bottom than on the spore-like blooms on the side of the pond. You can also get solutions to control algae from the same place you get your other koi pond supplies, preferably those made with barley straw extract, but keep in mind this should be followed by skimming and a 10-15 percent water change weekly, along with backwashing your filters. If you have a simpler labor-intensive type of filter, don’t clean the whole filter media during each maintenance period. You need to keep the bacteria alive, and hosing off all the filters will kill the good stuff.

Preventing Algae Bloom

Shade (or better yet—a correctly sized UV sterilizer) is the best weapon in your fight against algae bloom. If your pond gets more than three hours of direct sunlight each day, you’ll have to increase aeration and introduce floating plants that compete for nutrients. A few Asian algae eaters can also help in this regard because they’re voracious and will switch to fish food once they eliminate all algae.

If you need additional tips on controlling algae in your koi pond, reach out to Aquatic Warehouse. We carry everything you need to properly maintain your pond, from submersible pond pumps and filtration to lighting and nutritious koi food. Stop by our store in Kearny Mesa, order your supplies from our website, or give us a call at 858-467-9297 if you have any questions.