What to do about algae?


Algae control is often considered to be “the biggest headache in water gardening.” Let’s break this whole issue down, and then give you a real simple solution that you can take out into your own backyard and successfully expect to win the pea green soup war.  Algae can help balance the food chain in many ponds and waterscapes.   All it takes is a slight shift in balance, and can allow algae to take over, not only turning a pond into an eyesore, but wreaking havoc on the delicate ecosystem of a water environment.

Types of Algae
There are hundreds of types of algae throughout the world. However, the two types of algae that most water gardeners experience are suspended planktonic algae and filamentous (string) algae.

Planktonic algae consist of millions of microscopic algae floating throughout the water. This causes the water to turn green or “pea soup” color. Filamentous algae or string algae forms long and short hair-like strands. It attaches itself to rocks, gravel, plants, or any surface area it can find in the pond.

While the growth habits of algae may separate them from more traditional plants, they are still plants.   And like other plants, algae require the same elements to grow:  sunlight, nutrients and water.  You can’t control water but you can do something about the nutrients and sunlight.


Colder temperatures, such as in early spring and late fall, are typically advantageous for algae growth. Do not be discouraged during the colder seasons if your pond turns “pea soup” green or your have string algae problems. Be patient in the spring when your pond wakes up for the winter slumber,the pond will balance itself out.  The plants need to grow and the water needs to warm up in order to take up the bacteria you will begin to add to the pond.  We recommend a cold water bacteria at this time.

Ponds are like fine wine…they get better with age.

During colder temperatures there is an abundance of nutrients in the pond. The bacteria and plants that once kept the nutrients in balance are now dormant and algae will be the first to take advantage of these nutrients. The algae will be reduced as the bacteria and plants re-establish themselves and start using up their share of the nutrients. Some ponds take longer than others do, but your pond will once again be crystal clear and debris will noticeably diminish as the summer approaches.

Causes of excess algae

  1. Most common cause is too many fish for the pond size. Rule of thumb:  One inch of mature fish per one square foot of garden. Excess fish debris will feed the algae.
  2. Too few plants means the excess nutrients will continue to feed the algae. Plant coverage 60% of the pond surface
  3. Not establishing a colony of bacteria either through biological filters, BioBalls, and rocks and gravel in the pond.
  4. Excess sunlight – Use a pond dye if you can’t add the plants.
  5. Run off into your pond. Surrounding landscape can run into the pond bring fertilizer and extra nutrients into your pond.
  6. Don’t over feed the fish.  Once a day feeding is OK but feed them only the amount that they can eat in a few minutes.
  7. Leaks in the pond. Fix all leaks.

Solutions to treating algae including controlling string algae

Our solution to algae control is the IonGen available from Aquascape to combat both kinds of algae. Reduces the amount of treatments needed to keep the water clear. Can be used in conjunction with some bacteria treatments. Saves $$$ on treatments.


This is a fairly new water clarifier solution for ponds, Pondless® Waterfalls and other decorative water features. The IonGenTM drastically reduces pond maintenance and provides crystal clear water without the use of chemicals. A microprocessor inside the control panel causes the outermost atoms of copper, silver, and zinc to lose an electron, creating a positive ion. The positive ion attempts to flow from one of the bars of the Probe to the other and is swept away by the flow of the water where the ion can begin to treat the water. The IonGen™ Probe is self cleaning, using reverse polarity to prevent scale and debris build-up on the bars of the Probe. The metal alloys in the Probe are scientifically blended and tested to produce maximum results. The IonGen™ System is safe for fish and plants and is not toxic to any animals that may drink from the pond.

Easy to install
Install the Aquascape IonGen™ flow chamber directly into the water feature plumbing or hide the chamber underwater in an area with significant water flow. Can be placed in the skimmer.


  • Easy to use touch pad makes it simple to adjust the amount of ionization. Can be easily adjusted based on size of pond or water feature.
  • Electronic indicator automatically notifies you when the probe needs replacing. The probe typically last 1 to 3 seasons depending on usage, quantity of water and water parameters of the water feature.
  • Comes complete with electronic control panel, outdoor-rated transformer, 2 inch PVC flow chamber with replaceable probe, copper test kit and owners manual.

UV Light Sterilization  You see, the second group of manufacturers have evolved in the water gardening field from the swimming pool industry where chemical sterilization is seen as necessary. But, you don’t have a swimming pool but rather a water garden. Sure, occasionally you get in your pond to prune plants or say hi to the Koi. For decades, the public has been taking a dip in lakes and rivers and oceans without worrying about sterilization. Furthermore, sterilization, whether it’s from chemicals or UV Light Sterilizers, will cause you more problems than you can ever resolve this way.

UV Light Sterilization also kills the good algae and then the algae floats to the bottom of the pond and disintegrates. And during the disintegration process, it releases all of its stored nutrients. With this release of nutrients, guess what comes back in spades…algae! Next, you become dependent on these so called solutions.

Chemical treatment does kill the algae and should only be used in severe conditions. Your pond can become dependent on the treatment and the algae will come back in abundance. We recommend you use a product to clean up the rocks but first physically removing the debris by cutting the string algae off the rocks leaving only the part attached to the rock before using the treatment on the waterfall rocks.  After you have used the treatment, then if you want to use an algaecide you can but remember always to use one that does not hurt your fish or plants. You must check the label.  We recommend Microbe-Life Algaway 5.4 and the algae control products.

If you want to treat the algae with a chemical algaecide then it is best to use bacteria treatments of bacteria a few days after the chemical has been added. Bacteria can be added daily until the algae gets under control without any problems.  Do not treat with bacteria and an algaecide on the same day.  A bacteria enzyme is never considered a chemical.  Bacteria products are a natural product.

Beneficial bacteria plays an enormous role in balancing the pond and providing you with a low maintenance water garden. Bacteria enzymes should be added to the pond throughout the growing season. Bacteria will compete with the algae in the pond for excess nutrients, essentially starving off the algae. Bacteria enzymes are not chemicals but a natural ingredient for your pond.

Go to Water Treatments for a look at the products.


The BIOFALLS MATS are designed to be CLEANED ONCE A YEAR, typically in the spring. The debris and sediment that builds up in the BIOFALLS in the summer and fall is natural and should be left as is.

Routinely cleaning the biological filter may actually cause more algae by greatly reducing the beneficial bacteria growing on the filter mats and lava rocks.

We now recommend using the BioBalls instead of the lava rock as the BioBallsTM provide over 30 sq. inches of surface area per piece for beneficial bacteria to attach to. One set has 100 pieces in set. Micro ponds use one set, Mini size biological filter uses two sets and Standard size filter use 4 sets.

The following two products are a two step procedure that will keep you pond clean of debris that builds up on the rocks and pond. Just remember you can do away with all the products except the bacteria if you install an IonGen™.

First…for the stream and waterfalls…

EcoBlastTM rid the streams and waterfalls of debris. To apply there products, shut down the waterfall and sprinkle directly on the built up debris (cut off excess algae with scissors first), let it set for an hour and then turn your waterfall back on and it will flush the debris off the rocks. Less work…no sweat. Never leave your system shut down over night as this will deplete your system of oxygen.

Second…for the pond

S.A.B.TM is formulated to help reduce pond maintenance and promote the growth of beneficial bacteria and enzymes. S.A.B. will assist in the breakdown and reduction of debris in the stream, waterfalls, and pond. S.A.B. works by adjusting the micro-nutrients in the water of the pond resulting in conditions that are unfavorable for build up of debris. Use this once a month to back up the EcoBlast.


Plants, since they directly compete with algae for nutrients and sunlight, are probably the most important addition to your pond. Add a wide variety of plants to your pond. This not only creates a natural look, but also will help reduce the algae in different areas of your pond. Read the pond planning article for the suggested number of plants to use in a specific size water garden.

Place water hyacinth and water lettuce in your biological filter. These floating plants reproduce rapidly using up enormous amounts of nutrients. A monofilament fishing line or long stick (small bamboo) placed across the front of the biological filter will prevent the plants from flowing over the front of the waterfalls. Remove the older floaters when they start to over-run your biological filter. They are great nutrient rich compost for your garden. Note: too many in the biological filters can cause the water to run off the back of the filter.  Thin them out frequently.

NOTE: These floating plants can be invasive in warmer climates and are illegal in several states.

Plenty of bog and marginal plants should be added to the pond. Plants such as  Dwarf Cattails and Iris take up large quantities of nutrients. They are hardy and will be back each spring to help you balance your pond. Check under planning your pond for the right number for your pond.

Cattails can be invasive so keep these in a pot and don’t plant the yellow iris.

Cover 60 to 70% of the water surface of the pond by planting lilies. Lily pads float on the top of the pond soaking up the warm sunlight. The lily pads will reduce algae by preventing sunlight from reaching the deeper portions of the pond.  Lilies are also considered oxygenators.

Don’t overlook oxygenators! They soak up nutrients and sunlight directly through their leaves. Think of them as nutrient sponges. Look at the article on planning your pond for the right proportion to your size pond.  Such plants like hornwort, anacharis and parrot’s feather.

PHYSICAL REMOVAL: Physically remove clumps of string algae if it begins to over take the pond. Pull or cut away the algae where it is attached. Think it as “weeding the pond.”  Again the IonGen will take care of the string algae and you won’t have to remove the string algae from the pond because there should be none.

KOI: Adding Koi over 10 inches in length will greatly reduce string algae. The Koi, if not overfed on commercial food, will graze on the string algae attached to the rocks in the pond.


Only feed the fish the amount of food that they will consume within a few minutes. Fish food that is not eaten by fish will decompose in the pond and increase nutrient levels. If excess algae conditions exist, reduce or eliminate feeding fish for a while. You can begin to feed the fish again once all algae is under control.  Koi will always eat and appear hungry but be careful not to overfed as overfeeding can cause an ammonia problem.


Tap water can have an abundant amount of nutrients in it. Continually adding large quantities of tap water to compensate for a leak can actually promote algae growth.

Have a leak…need some advice…See Article on Troubleshooting Leaks.


Never use lawn fertilizer or insecticides on plants around your pond or on areas of your property that will drain towards your pond. Lawn fertilizer and insecticides will cause large algae blooms, as well as, severely threaten the aquatic life inside your pond.


Keep your pond free of debris. Don’t let the skimmer debris net over-fill with leaves. Decaying leaves and seeds in the skimmer will contribute to unwanted nutrients. Net all ponds located in a tree area.


The rocks and gravel which give the pond a natural appearance not only cover up the black liner, but also provide a home for the beneficial bacteria to reside. Plant debris, fish waste, and decaying organic matter that don’t get swept into the skimmer will drop to the bottom of the pond and rest on top of the rocks and gravel. The bacteria living among the gravel can then go to work breaking down the waste and debris.

Now if you take all 5 elements of an ecosystem…

  • Filtration System
  • Rocks and Gravel
  • Recirculation System
  • Fish
  • Aquatic Plants

and mix them up in the right proportions, your water will be naturally crystal clear without resorting to any artificial means to do it. Equally important, the time you spend maintaining your pond will be reduced to a bare minimum (5-10 minutes a week), while your relation time you have to spend with family and friends will be maximized.

Happy Pondering,

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