Pond Algae in Summer
  and How to Get Rid of it Naturally


How to Handle Algae Problems in Summer

Many pond owners experience the dreaded problem of algae blooms in various forms, especially in the warmer summer months when the sun is strong and people are feeding their fish more often than usual

Algae blooms come in various forms, from long stringy (or hair) algae, to green 'pea soup' water. I've experienced them all, but this year I had a new kind of algae bloom that proved especially difficult to get rid of.

As you can see in the pictures below, floating islands of algae started to appear in my pond last month. I tried skimming them out, vacuuming them out, vacuuming the bottom of the pond, reducing the feeding... just about everything. But I had little success.

I noticed also that these 'islands of algae' would disappear at night and early morning, but would then mysteriously re-appear in the warmer hours of the day, once the sunlight hit.


I was able to see an accumulation of algae on the bottom of the pond, that would 'settle' there during the night but then float again the next day. Clearly I had to attack the source of this algae, whether it was excess nutrients in the pond, too much sunlight, poor filtration, low oxygen, or all of the above.

It's always to attack the root of the problem with as may resources ad you have, so in this case I did everything I could think of.

To start, I noticed that my one remaining water lily was in need of dividing and repotting, which would be helpful because then I could spread out the coverage from the lily pads in the pond.


As a general rule in most water gardens, you want to have around 70%-80% surface coverage to keep the sunlight from creating algae issues. In a KOI pond, this is not always practical, but every bit helps... especially down here in Florida where the sun is especially strong.

So I pulled out the lily, and as you can see below it was long overdue for a dividing and repotting procedure.


First, I removed the lily from the mesh pot I was using (I like mesh 'pots' that let the roots absorb water nutrients from the water all over, not just from the top. Plastic tubs don't allow this, and mesh pots can also be wrapped over the top to keep the fish from burrowing). 

Here I used a regular garden pruner to cut the lily roots into more manageable sized tubers for repotting. When I was finished, I had more than enough so I selected the best ones, that already had lily leaves growing from them.


After isolating these, I gathered more mesh pots, added some garden soil from my yard (which is sort of a sand / soil mixture down here in FL, but can also be heavier clay from up north depending on where you live).


Then I added some Lily Gro fertilizer to the pots in the soil to help jump-start the lily growth once we repotted them.


Next, add the new tubers to the pots, and put about 2" of fresh soil over them, and pack it down with your fists or fingers.


I also added several of the tubers to each pot, making sure there was plenty of soil for them to grow into and not to overcrowd each one, but I wanted to give them several chances to grow and get big quickly so I would shield as much sun as possible in the pond.


Once repotted, I used cable ties to wrap the mesh sides over the soil to prevent the large KOI from burrowing into the plants, which they love to do.


As you can see, I was able to create 3 new lilies from my original overgrown lily above.


Once all 3 were repotted, I placed them in the pond in several areas that seemed to be getting the most sun, and away from the waterfalls. Water lilies prefer calm water, and will grow best under these circumstances.

The purpose again of adding the water lilies is to have them grow many lily pads that will cover the surface of the pond and block the sunlight from hitting the water and causing more algae growth.

Next, I added some submerged plants called Anachris. These are excellent for absorbing excess nutrients from the pond, and were my secret weapon for years when I had a water garden center and we cleaned over 100 ponds per season.

We used to put Anachris in every pond we cleaned, and it kept the water clear all summer long. As a general rule, you want to have around 10 bunches of Anachris (Hornwort, and Camboba works well also) per 100 gallons of water. I like to bunch all 10 together with a rubber band, and pot them in sand with gravel on top, just to weight them at the bottom of the pond.


As you can see here though, these are not in the pond at all, but in the upper reservoir of my waterfall. When you have large koi (anything over 6" actually) you don't want to have these plants in your pond as they will eat them and make a real mess in the pond, which we don't want.

I ordered 100 bunches of Anachris from Springdale Water Gardens, and put all 100 bunches (in bundles of 10 bunches together) in my waterfall. This will ensure that they get maximum exposure to nutrient-rich water and essentially 'filter' the water of nutrients 24 hours a day.

Another thing I noticed is that my algae problem started when I switched my KOI food from a higher quality brand like Hikari to less expensive Tetra food. I suspect that there is something in the Tetra food that was causing excess nutrient levels in the pond, from the fish waste or possibly uneaten food.

Hikari Spirulina Fish Food  Hikari Wheat-Germ Fish Food

So I switched back to Hikari Koi Food which is a better quality food, made from better quality ingredients. I've used Hikari for years, and never had problems with clouding the water and my fish have never looked better!

Now excess algae can also be caused by or at least worsened by lack of adequate oxygen in the pond, especially at the bottom. That's why they usually have large aerators and fountains in large lakes too big for traditional filtration.

So the next thing I did was to upgrade my air pump, to add more oxygen to the pond (which is always a good idea, and the fish will thank you for).

Here you see my new air pump, a real work horse! My last one lasted for years, but finally died about a month ago (strangely just around the time the algae started to appear also).

I picked up this pump at a KOI show, and got a great deal because I waited until the end of the show and offered the vendor $45 for this $75 pump. He didn't want to pack it up and take it home, so he agreed. this pump should last me for another 5 years, so it was worth the $45 easily.

Proper aeration is important for a pond for many reasons, including fish health primarily. Excess algae in a pond can actually be dangerous to fish in low oxygen environments or with heavy fish loads because at night, plants and algae actually absorb oxygen and give off CO2 - the opposite of what they do during the day.

So with heavy algae blooms, at night all this algae can cause dangerous drops in oxygen levels at night. This is most dangerous in the morning when oxygen levels are the lowest, after a long night of oxygen depletion from the algae, and when the sun hits the water and raises the temperature.

Warmer pond water holds less oxygen, another reason why it's so important to properly aerate your pond in the summer.

Years ago, when I was taking care of the 50,000 gallon 'pond' at the Embassy of Japan in Washington DC (don't ask me why they didn't know how to care for their pond, they supposedly invented koi keeping, but that's a different story). I received a phone call one day, saying that all their fish were dying. After extensive testing of the pond water, I determined that there was a sudden drop in oxygen levels during the particularly hot summer weekend, caused by an extreme algae bloom in the shallow pond that resulted in the fish actually suffocating in their own pond water.

Don't let this happen to you!

The other major area that I needed to address was my filtration.

My skimmer pump had become so clogged, that the flow was reduced by 50% and so it was not adequately skimming this floating algae off the top of the pond like it should have been. Skimmers are great for this, so if you don't have one, I highly recommend putting one in.

Lastly, I was having some problems with my Aquabead filter. It's been a fantastic filter over the years, and kept my water crystal clear always, but lately it was not doing the job and I was having to backflush it 3 times a week! 

But fortunately the smart folks at Aquabead have just come out with a new filter media that does not clog up (ever) and keeps the water just as clear.

They also have an upgrade kit for converting your old Aquabead filter to the new Alpha One media. To watch a video I just made on how to do this conversion, click here to watch the video.

*Aquabead Owners - Click here to watch the upgrade video

As you can see below, all the hard work paid off!

My pond is now crystal clear again (and staying that way thanks to my new Alpha One filter).  All the plants are also helping to cut down on the nutrient load and reduce sunlight in the pond, which contribute the most to the algae growth in the first place.

So the pond looks great, and now I only have to back flush the filter once a week or every two weeks - a huge improvement from before. Thanks to Gary Cryer at GcTEK, the manufacturer of Aquabead filters.

To get crystal clear water like this in your pond, have a look at our line of biological bead filters for all sized ponds here. Of course, I am partial to my Aquabead, which is now an Alpha One filter after the conversion.

Here is the link again to have a look at these amazing new pond filters:

Alpha One Pond Filter Systems:

Alpha One Pond Filters:

Here are some more pictures of my pond, with nice surface coverage from the water lilies, which took about 2 weeks to grow back after being repotted.



The pond is looking better than ever, thanks to a good overhaul of the filter, nutrient absorbing submerged plants, more surface covering water lilies, the addition of a new air pump to aerate the water, cleaning the skimmer pump for greater skimming power, and by changing the food and cutting down on the number of feedings to also reduce the nutrient load in the pond.

That's all for this month.

Happy Pondkeeping!

Brett Fogle, President and
Head Pondkeeper At Large
MacArthur Water Gardens

    More Pond Articles

  MacArthur Water Gardens Home | Site Map

MacArthur Water Gardens 2004
PO Box 3628 | Alpharetta, GA 30023-3628