Everything You Need to Know About Algae

algae in your backyard pond

We highly recommend you bring a photo of your pond as well as a water sample to our store. We will give a free water analysis and guide you through the necessary steps to clearing your algae. You'll even leave with a personalized step-by-step treatment brochure. 


Algae is a very broad term for hundreds of thousands of species. You'd be surprised how many species there are in our ponds alone! For our purposes, we group algae into three main groups:

green water algae backyard pond
Single-celled algae at its finest!

Single-Celled Algae -- Causes green water, looks like pea soup or a deep forest green color

string aglae in creek backyard pond
That's a healthy crop of string algae!

String Algae -- Anything you can touch or see floating on the surface is called "string algae."

carpet algae backyard pond
This slight green coating on these rocks is perfect!

Carpet Algae -- The very light green coating on your rocks. (This stuff is GREAT! And we want to keep it! Find out why below.)


Let's talk about how algae grows. We're going to break down the Nitrogen cycle in very simple terms for our purposes.

  • Organic waste (fish food, fish poo, dead plant leaves, dead tree leaves, etc.) break down into ammonia. Ammonia is useless and toxic.

  • Bacteria breaks ammonia into nitrites. mostly useless still but way less toxic.

  • Bacteria further breaks down nitrites into nitrates. Hey, now we have something useful! High levels can still be dangerous, but nitrates are something that can be consumed by plants.

So where a pond can go "wrong" is somewhere in this cycle. If this is imbalanced in any way, then the pond will look like a mess. It will be bright green or have crazy amounts of string algae. We're going to break down the cycle step-by-step and follow where you can go "wrong."


Step 1-- Limit organic waste build-up.

Fish Feeding
Feeding your fish too often or with foods full of waste can wreak havoc on your water. Read more here.

feeding fish
Feeding your fish is fun-- just do it responsibly!
Fish Population
The general rule of thumb is 1" of fish per 10 gallons of water. Are you overpopulated already? Find out what to do with your extra fish here.

cleaning backyard pond
Most ponds benefit from annual cleanings.

Step 2 -- Boost your aerobic bacteria.

We love our aerobic bacteria! Most of what we do in building and maintaining a pond is to foster the growth of those beneficial bacteria colonies. 

backyard pond aerator
This is our most popular model of aeration system, the PA4.

You need oxygen for your aerobic bacteria! Your waterfall or spitter are not doing you any justice, either. Read more about the right type of aeration here.

treatments for clear water for backyard ponds
We add treatments weekly.
Using The Right Bacteria
We've used a ton of different beneficial bacteria in the pond market. I mean a TON. We know what's out there. We know what is a waste of money, and we know what's not. The bacteria we sell is what we use exclusively, even in our own personal ponds!

Surface Area
Bacteria needs somewhere to grow, right? Our ponds provide surface area with river rock and biological filtration. Need help finding the right filter for your own pond? Stop in and we'll set you up. 

Step 3 -- Have lots of aquatic plants.

If you don't have aquatic plants, then even if you follow every step listed above, you will still struggle with algae. Because guess what? Algae eats nutrients just like other plants! By having aquatic plants, you are staving the algae!

backyard pond plants
Pickerel weed is a native aquatic marginal. Isn't it beautiful?

Certain types of aquatic plants are great at competing with algae for nutrients:  floating plants (water hyacinth and water lettuce) and marginals. Marginal plants grow in the shallow areas of the pond.

Notice that water lilies did not make this list. Water lilies are NOT great to combat algae.

We have a ton of resources for aquatic plants here, but if you really want to get the best idea of what's available, stop in the shop and check out the selection. You'll be surprised how many different types of blooms, heights, and colors are available!


Additional Info About Specific Types of Algae:

Single-Celled Algae (Green Water)

This type of algae is potentially dangerous for your fish in the warm summer months. It pulls oxygen from the water and can suffocate your fish. 

If you have this algae, do not use any treatments for string algae! Including ones we normally prescribe. 

String Algae

There is an additional product we use with our bacteria to help quell unruly string algae: Remove Away Plus. No, this is NOT an algaecide! Algaecides are a BIG no-no for us. Yes, they kill algae, and they do so very quickly. Once that dead algae begins decaying all at once, it sucks oxygen from the water. This can (and has, in many of our poor customers' experiences) kill off entire populations of fish! Scary stuff.

Instead, we use a natural enzyme, which prohibits the algae from eating. It slowly starves the algae, and it dies off gradually. The bacteria you're using will help break it down into plant food.

Carpet Algae

This is an algae we want to have! Every pond should have a light, fuzzy coating on the rocks. It helps keep your water crystal clear, as it acts like a big "plant." Many, many times we will have people complain of green water, and it boils down to them not having an adequate layer of carpet algae!

Remember this if you remember anything...
Green Rocks == Clear Water
A formula for success!


clear backyard pond

Having a clear, beautiful pond is attainable! You don't have to live with algae. We've helped thousands of pond owners improve and maintain their ponds, and we can help you too.


Popular Posts