How to Treat Pond Algae – 5 Things to Consider

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Algae are considered invasive due to their resilience, high spread rate, and effect on the surrounding fauna and flora. Interestingly enough, algae will spread and grow in all aquatic environments, no matter how careful you are about preventing them.

They will grow in aquariums without any connection to the outside world, as long as the ideal conditions arise. Needless to say, the risk of experiencing an algae invasion is even higher in outdoor setups like ponds.

So, today we will discuss pond algae and how to counter and prevent them effectively. Which is difficult enough as it is.

7 Ways to Treat and Control Pond Algae

There’s a saying – Nobody wants algae, but everybody will get them. Yea, I just made it up. But it presents an interesting point, and that’s that you need to be ready. Your pond will eventually face an algae invasion if you’re not mindful about it.

Fortunately, there are ways to counter pond algae effectively and even prevent them from reoccurring to some point. Here are 7 great tactics to employ to your aid:

Shade with Plants

Algae love sunlight. The brighter it is, the faster the algae will grow and spread. It’s only natural that they don’t fair so well in shade; this is where you come in. It may be difficult to create shade around your pond without also impacting the plant population present in the pond as well.

Not to mention, the act will require some work time and crafting or buying some rather large elements to keep the pond area in constant shade. Fortunately, there’s an easier way to achieve that – you add more live plants to your pond. These will always grow taller, casting a much-needed shade on the aquatic life below.

The result is fewer algae because the plants will essentially restrict their access to sunlight and cause them to starve to death.

Then there’s the point of nutrient competitivity. Plants and algae compete over pretty much the same resources. In conclusion, the more plants you have, the fewer the algae present in the environment. Just ensure that your plants get sufficient nutrients, adequate CO2 and benefit from ideal conditions to prevent algae from taking over.

UVC Lamp

UVC is a form of radiation on the light spectrum that is mostly absorbed by the Earth’s upper atmosphere. Which is a good thing, seeing that it’s highly hazardous for mostly all life forms, depending on its concentration, of course. We know that UVC is lethal to microorganisms like bacteria, mold, germs, and, what do you know, algae.

Fortunately, you don’t need to rely on mother nature to deal with the problem since it probably won’t. There isn’t enough UVC in sunlight to disturb the algae population. This is where UVC lamps come in to fix the problem for you. These tools are ideal for algae removal in both closed systems like aquariums and open systems like ponds.

Naturally, the problem is that UVC lamps aren’t exactly ideal for plants and fish, so caution is advised. Use the lamp according to its instructions, and make sure that the intensity doesn’t affect the pond’s fauna or flora.

Pond Algaecide

Pond algaecides make up for the most comfortable and effective algae-control method available. They’re readily available for sell all over the market and, depending which one you’re getting, they can be extremely effective at the job.

  • The best pond algaecides available will:
  • Inhibit and eliminate the algae population effectively
  • Handle various species and strains of algae at the same time, including hair algae, green hair algae, blanketweed algae, etc.
  • They won’t affect the fish or plants in the habitat
  • They promote beneficial bacterial development
  • Weekly controlled use will prevent algae from returning and keep the environment cleaner and healthier
  • You can use them in conjunction with water conditioners and other products to treat fish diseases and promote fish health
  • They lower the need for tank and pond maintenance related to algae bloom

Naturally, you must first understand the type of algae you’re dealing with. Only then can you decide on the perfect algaecide for that specific algae species. And make sure not to use any algaecide if your pond houses any crustaceans like snails, shrimps, or lobsters. These creatures are overly sensitive to the chemicals contained in the products.

Good Filtration

You need adequate filtration if you want your pond water to remain clean and algae-free. That’s because algae hate flowing waters, whereas fish and plants love it. Provided it’s a manageable flow, of course.

So, a filtration system is necessary to counter the algae and make it more difficult for them to spread over time.

Sodium Percarbonate

Sodium percarbonate has many roles, such as cleaning agent, stain remover, home deodorant, and, fortunately, disinfectant. You’re probably more interested in the latter, for obvious reasons. Sodium percarbonate is an excellent antimicrobial and algae killer that will eliminate a variety of dangerous pathogens. These include viruses, mold, bacteria, algae, fungi, and any other harmful microorganisms.

Make sure you personalize your use of sodium percarbonate to your specific situation. The pond’s size, the available plants and aquatic life, the type of algae, and the severity of your algae spread will all influence the amount of sodium percarbonate to use. I recommend discussing this situation with your vet before using the chemical to ensure it doesn’t impact your aquatic life.

It generally won’t take longer than one week to eradicate the entire algae population.

Manual Removal

This is a necessary step in cases of severe algae infestation. You should remove the excess algae manually, if possible, trying not to disturb the pond life in the process. Rakes and skimmers are great tools in this sense, allowing you to both eliminate mature algae and eradicate younger cultures before they spread too much.

Algae Eaters

This is a preventive method more than a treatment-like one. The goal is to control the algae population to prevent it from taking over the pond. To achieve that, rely on algae eaters, which come in various forms, sizes, and temperaments. You can opt for fish, crustaceans, snails, and pretty much anything that eats algae, no matter the appetite.

These creatures will feed on the available algae population daily if sufficient algae are available.

Remember, don’t rely on algae eaters to control the algae population themselves. The optimal way to control algae is to employ different control mechanisms at the same time. This will increase your chances of successfully preventing algae, considering that algae are quite hardy and resilient organisms capable of thriving in various adverse conditions.

How Long it Takes to Get Rid of Pond Algae?

It generally takes approximately a week to eradicate the algae population via one or several control techniques. However, it depends on how effective the removal method is. Sodium percarbonate will deliver optimal results within a week, but other methods may last longer.

What Fish Eat Pond Algae?

The koi, grass carp, Siamese algae eater, bristlenose pleco, and mosquitofish are some of the best algae eaters around. You can find a variety of other algae-eating species as well, provided you keep in mind the following tips:

  • Make sure that the fish are compatible – It’s of no use to have several species of algae eaters if one species is prey for the other. The fish will eat each other, sabotaging your efforts during the process.
  • Size matters – All pond inhabitants need to be of similar size. This way, you will prevent bullying, constant attacks, and even death, all of which are natural when pairing large and small fish.
  • Be careful about bottom dwellersBottom dwellers have the unpleasant habit of digging around the substrate and muddying the water. So, keep an eye on that. A sand or gravel substrate will make less mess than soil, although those also come with downsides. Choose wisely!

Is Algae Bad for Ponds?

Yes, algae is bad for ponds. I would say it’s worse for ponds than it is for indoor aquariums simply because it’s more difficult to control and combat. Outdoor algae have a larger environment to spread and have access to natural sunlight. They will thrive when ignored, spread faster, and grow larger than those infesting indoor setups.

A pond algae overgrowth will restrict sunlight from reaching the deeper layers of the pond, which will directly affect fish and submerged plants. So, a good algae-prevention system is necessary to prevent that. This includes a filtration system, a group of algae eaters, sunlight control, CO2 management, live plants, etc. In other words, whatever gives you an upper hand in the game.


Algae are pests capable of invading and destroying entire ecosystems when ignored. Fortunately, they have a variety of weaknesses that you can take advantage of.

Follow my guide, approach the situation intelligently, and you’ll get an algae-free pond for years to come.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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