As spring arrives the warmer weather and increased daylight hours awaken your pond, and new challenges arrive as your pond ecosystem begins again. The most common early spring challenge is the onset of string algae.
Before we get into troubleshooting the pesky menace let’s look over what it is.
What is String Algae?
String algae is a form of filamentous algae, a simple aquatic plant, with the most common being Spirogyra and Cladophora. Easy to recognize because it grows in mats usually in shallow, full sun locations. It is not harmful to your fish or the ecosystem, but can begin to choke out marginal and aquatic plants if not kept in check. Now this is important to my next point.
It is a symptom of a nutrient imbalance, most commonly excess phosphorous, so just removing it will not solve the issue of its growth. Generally it is to be expected, and in some cases, we build ponds with areas to encourage and control its growth such as a wetland filter. You can remove it by hand, but before you go about creating more work for yourself and chasing your tail lets look at possible causes.
Spring String Algae Culprits
Lets look at the variables that cause the nutrient imbalance, and find some simple troubleshooting techniques to cross them off the list.
1. Excess Water Loss.
If your pond has an autofill, and you have kept it running during the winter, there might be a simple leak in your waterfall or pond edge that is causing water to leave the closed system and be constantly replaced with new city or well water. This is a problem for many reasons, but lets focus on the nutrient imbalance. During the winter time the bacteria and aquatic meiofauna in your filter is dormant, and not working at optimum efficiency. So if we are constantly adding new, unfiltered water, there is a chance we are introducing nutrient rich water to your closed ecosystem. In addition to a low liner edge in your waterfall or pond edge look for wicking. Wicking is when there is soil or fabric touching the water and allowing the water in the pond to soak into the landscape. This is a capillary event that can allow a lot of water to escape the system.
2. Rainfall Runoff
Another culprit for your nutrient imbalance that is common is excess runoff from rain events dumping into the pond. With rainfall you can expect soil and other nutrients to be pushed into your closed ecosystem. Berming the edges of your pond and managing this runoff is crucial to preventing this variable from disrupting this balance. Otherwise if your neighbor treats their grass with fertilizer, and it rains, that can be running into your pond.
3. Overcrowding/ Overfeeding
Sometimes we get too carried away with our fish purchases, or they all fall madly in love and create countless generations. Unfortunately, there isn’t enough room for everyone. Of course this is dependent upon the size of the pond and the filtration and can only be addressed on a case by case basis. Fish produce ammonia and nitrogenous waste that is generally broken down by bacteria and aquatic meiofauna. As discussed above those critters are dormant, so overcrowding is more prevalent during the cooler months and into the spring. Overfeeding only increases this issue as those nutrients become trapped inside the pond and during the winter are only feeding excess algae.
4. Inadequate Biological Filtration
Overcrowding and overfeeding can be alleviated by upgrading your biological filtration. You can follow manufacturers recommendations, but generally I cut those recommendations in half. For example, Aquascape recommends the BioFalls 6000 for ponds up to 6000 gallons. I cut that in half, and recommend the 6000 for a 3000 gallon pond. This allows buffer room and reduces boom and bust cycles throughout the season. Maybe your biological filtration follows these guidelines, and we need to look at your mechanical filtration, circulation, and aeration requirements. Again this is a case by case basis.
5. Excess Debris
Into the next form of filtration, mechanical filtration. This is your simple skimmer, or if you have a larger pond, an intake bay. Generally when leaves fall into the pond they become waterlogged and sink to the bottom. They then decay and release nutrients into the water column. We want to limit this variable as much as possible. This is why the design of your pond is so important. We want the pond to be able to circulate water in such a way that any falling debris is quickly pushed to a skimming area where it can be removed. Of course no design is perfect. There will undoubtable be ‘dead areas’ where even circulation jets fail to pull everything towards the skimmer.
String Algae Solutions
Now we know what string algae is, what causes it, and a few troubleshooting steps to limiting the variables. Lets explore some proactive steps you can take on top of what we have learned already.
1. Spring Clean Out
This is the simplest and almost always necessary step even if you don’t have string algae. Removing leaf debris, decayed aquatic plants, and excess detritus is the simplest way to preventing nutrients from feeding string algae.
2. Aquatic, Marginal, and Floating Plants
Adding plants is the easiest way to reduce the amount of nutrients in the water column. We call this ‘competitive exclusion.’ The beautiful plants you want consume all of the nutrients and leave nothing left for not only string algae, but also floating algae.
3. Bacteria
Keeping a strict regiment of adding beneficial bacteria is essential to seeding your biological filtration with the right enzymes to encourage we get the most efficient strains of nitrifying bacteria thriving in your pond. Adding an autodoser makes this task automatic and ensures you never forget another treatment.
4. Sunlight Exclusion
Another technique we can employ is straight up starving the pond from sunlight. This can be achieved in many ways, from encouraging floating plants like lillies, hyacinth, and water lettuce, to planting bushes and trees to shade the pond, shade cloth, or even hardscape elements such as pergolas or gazebos with new seating areas. Generally this is best done with the pond design in mind, but can be incorporated after.
Now that you have the majority of the causes and troubleshooting techniques I hope you can execute and help alleviate that pesky weed so that you and your family can continue to enjoy your aquatic paradise.
If you are interested in getting professional help with your algae woes, or you are interested in building a pond the right way and circumvent these issues from happening to your future pond plans give me a shout and fill out the contact form.