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