Controlling String Algae in your Pond

June is the time of year when pond owners often call us up with questions or concerns about the string algae growing in their water feature.  It can show up seemingly overnight, and without a solid plan of action, controlling it can become a regular chore.  Fortunately, there are several proven measures you can take to combat the stuff, and there are quite a few products available that are designed to assist with that task.  The main problem then seems to be a lack of education on how to use those products, and a misunderstanding of what causes string algae and the role it plays in an aquatic ecosystem.  

Click 'Read More' down on the right to learn how the pros deal with string algae...

String algae can really impair visibility in your pond.

The key word here is ecosystem.  Our approach to water gardens has always been to create a naturalistic feature that adopts the same philosophy and principles that are found in nature, and to use the tools given to us by nature to duplicate those processes in our man-made water gardens. The way we do this is by first identifying what is going on in a natural stream or pond, and then making sure we do the same things in our own creations.  

String algae is part of nature, and it does serve an important function.  It is an effective bio-filter, and like clams or mussels, it purifies the water where it lives.  Unlike clams or mussels, it also acts as a mechanical filter, straining the water that passes through it and capturing some of the silt and debris that would otherwise cloud your water.  Another function of string algae is as a food source for many of the animals that live in your pond.  Not only will various animals use it for sustenance, they can also use it for shade and shelter.  Frogs like to lay their eggs near string algae to keep the tadpoles hidden from predators.  The same goes for small fish and some species of insects.  Despite these benefits, it can still be a nuisance for pond owners when it grows out of control.  

One way to combat string algae is with the use of an Autodoser.  This is a tool designed to release a slow and steady stream of a prescribed water treatment at the proper rate for your pond.  There are a variety of treatments available for use with an Autodoser, each designed for specific occasions.  The one we recommend for controlling string algae is called Maintain for Ponds, this mixture contains a combination of beneficial bacteria, enzymes, and a powerful phosphate binder to reduce pond maintenance and maintain crystal-clear water quality.  Other treatments for the Autodoser are useful for breaking down sludge and organic debris, for safely and gently clearing discolored water, and for promoting fish health and reducing stress after a clean-out, but the Maintain treatment is easily the most popular and we have seen excellent results in ponds treated with it.  

Dosing your pond with bacteria and enzymes is a valuable preventative measure when battling string algae.  The bacteria consumes nutrients in the pond that would otherwise sit dormant as sludge, like an all-you-can-eat buffet for algae.  To really make a difference you'll want to combine these treatments with some good ol' manpower.  

Despite advances in pond science and innovative new products, the most effective way to quickly clear string algae from your pond is still the old-fashioned method of pulling it out by hand.  This removal method will eliminate the bulk of the algae from the water, and prevent it from breaking down into nutrient-filled sludge that would otherwise fuel a new round of algae growth. ​

Debris in the pond or stream breaks down into nutrient-rich sludge, where it fuels another round of algae growth...

When you are pulling the algae from the pond, you'll find it mostly comes right out, except for where it is attached to the rocks.  It likes to anchor itself to rocks and other structure in the pond, and these bonds can be quite strong.  More than once, I've pulled out some string algae with a small stone or two attached to which the algae had anchored.  Removing the algae from every pebble on the pond floor can be a time-consuming task; to make it easier we recommend using a long brush with stiff bristles to scrub the algae off of rocks, especially along the waterfall where it often forms long flowing strands that reach down into the pond or basin.  A nice trick here is using the brush like a spaghetti fork, spinning the algae onto the brush to collect it in more manageable clumps.  Sometimes the algae appears like a bubbly crust on the surface, then when you go to remove it you discover it stretching out like the cheese in a gooey mozzarella stick.  The brush trick is great for getting a grip on the algae and keeping it from dripping green slime onto the rocks or landscaping along your pond.  
 
A long-handled brush can be useful for reaching the deeper parts of your pond, and for retrieving string algae that is in less accessible areas.  Depending on the size of your pond, you may have to wade into the water to get to all of it.  A long handle to hold can serve double purpose in this scenario, helping you keep your balance on wet, slippery rocks.  

We generally avoid the use of algaecide in our ponds.  It does not treat the cause of algae, which is excess nutrients, it just kills off the existing algae, which only adds to the nutrient load in the pond.  As you might imagine, that would lead to an even larger algae bloom next time, which could be as soon as a week or two later.  The one time we might make an exception is in a pondless waterfall system without any fish.  In those cases, after scrubbing with a brush and removing whatever algae we can get by hand, we would shut off the waterfall pump for about 15 minutes and apply EcoBlast / Rock & Waterfall Cleaner to affected areas where the string algae is anchored to the pond.  This stuff is most useful when the algae has covered entire rocks and it has become impractical to remove it all by hand.  

Once you've cleaned the algae from your pond and have applied treatments to restore the balance of the ecosystem, you should consider whether your pond has enough plants.  This is perhaps the single most important consideration when it comes to finding harmony in your pond.  The right amount of plants depends on how much nutrients your pond is producing and accumulating.  Not enough plants to convert those nutrients into foliage and flowers is a guaranteed way to develop an algae problem.  If you have a lot of fish, they will be making lots of fertilizer, and you'll want more plants.  If your pond is downhill from manicured lawns and landscapes, there is a possibility it collects runoff fertilizer.  If so, you'll probably need more plants to account for the additional nutrients in the fertilizers, but if it's really bad you may want to consider redesigning the pond or surrounding landscape to redirect the drainage away from the pond.  

There are two more tools that are often used with the intention of eliminating algae: the UV Clarifier, and the copper IonGen.  These each have a specific function in the pond, and can be quite helpful when used correctly.  It is important to understand how these tools work, because if they are used incorrectly they can create their own problems in the aquatic ecosystem.  
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First, we'll discuss the UV Clarifier.  This tool is great for eliminating the green water that occurs with pea-soup (planktonic) algae blooms.  The UltraKlear UV Clarifier is basically a section of plumbing with a sleeve containing a T5 high-output UVC bulb.  The ultraviolet light emitted by this unit sterilizes the water passing over it, killing any single-celled algae.  It does a great job at preventing green water, but because it only treats the water passing through the sleeve, it's not effective against the multi-celled string algae that is rooted to the rocks or plants in your pond.  

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Next is the IonGen System, from Aquascape.  This system uses an electrified copper probe that safely releases copper ions into the water.  Copper is effective against algae of all types.  It works by binding to proteins in the plant and causing the cells to die.  It is quite effective at this, and if you look at the label of any algaecide, it's likely that some form of copper is the main ingredient.  The problem with copper-based treatments is that they are indiscriminate and will harm or kill more than just algae.  The other plants in your water garden can also be harmed by too much copper, as well as your fish.  In fact, copper can have a two-fold impact on your fish: first from direct exposure to copper salts that can build up in tissues to reach toxic levels, and second, from indirect oxygen starvation that can result from too much algae dying at once after a pond has been treated with copper ions or copper-based algaecide.  Of all the copper-based algae treatments on the market, the IonGen is one of the easiest to use.  It can be adjusted to fine-tune the amount of copper ions that are released, and it comes with a copper tester so you can ensure you are staying within safe parameters for your fish and plants.  It is very important to do these tests regularly when you are using the IonGen, because you want to find the 'Goldilocks' level of copper that is effective against algae but won't harm your fish.  The maximum concentration of copper that will not cause immediate problems for fish is just .25ppm, although some biologists say the fish will begin to feel discomfort at levels as low as .015ppm.  It can be difficult for us to know exactly what the fish are feeling, and with such a delicate balance to maintain, it should be easy to understand why we prefer to use other methods of algae control whenever possible.  Another potential negative side effect of copper-based treatments is destruction of beneficial bacteria.  The same thing that makes copper effective against algae also makes it harmful to the bacteria that we want in our ponds.  It would be counter-active to destroy the bacteria in an ecosystem just to get to the algae.  The algae tends to grow back faster than the bacteria, leaving the pond in worse shape than before, and prolonging the process of achieving a natural equilibrium in the ecosystem.  

When all the protocols are followed, and you've removed string algae by hand, added plants to recycle excess nutrients, cultivated healthy bacteria colonies in the pond and the bio-filter, and are applying appropriate treatments either by hand or via an AutoDoser, then you're on the path towards establishing a vibrant aquatic ecosystem.  Sometimes a new system takes weeks or even months before all of its parts are functioning together in harmony; the same goes for a pond that has just been fully cleaned for the first time in years.  The water chemistry may be out of balance, and the bacteria will need to reestablish themselves.  It is important to have patience during this period.  The biggest mistake people make when dealing with algae is to go overboard on the algaecides and neglect the other components of the pond that all contribute to a stable, happy and healthy environment.     

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