Unsightly Lyngbya on Surface
Lyngbya is a problematic aquatic growth that is common to many ponds in North Texas. It is not an aquatic plant nor a “true” algae, but actually a type of cyanobacteria that can be a pond owner’s worst nightmare. It ranges in color and usually appears green, brown, gray, or black. It can be isolated to small areas of a pond or it can cover the entire surface in a dense mat. More often than not, it collects on the downwind side of a pond.
This bothersome growth is most common in the summer months of July, August, and September and infects approximately 25% of the ponds in the DFW area. The problem with Lyngbya is that it is highly resistant to commonly used algaecides. There are a few products that can be used to manage the spread of Lyngbya; however, total eradication is virtually impossible without some help from Mother Nature.
Lyngbya initially forms as a dense, carpet-like layer on the bottom of the pond. The cyanobacteria produce gases which then cause pieces of the mat to break loose and float to the surface. It is slimy to the touch due to a gelatinous coating that it produces. This gelatinous coating that makes the Lyngbya resistant to algaecide applications. There are currently no products that have been proven to be 100% effective in penetrating this coating. Even when the coating is penetrated and the algaecide kills the internal cells, the mucus-like layer prevents the Lyngbya from decomposing and sinking to the bottom. In this case, you end up with dead, white or gray colored remnants that continue to float on the pond surface for weeks at a time.
The only way to manage the spread of Lyngbya is to try and change the conditions that favor its growth. Lyngbya thrives in shallow, clear water that has high amounts of nutrients (phosphorus and nitrogen) and little or no water movement. The use of an approved pond colorant is the best way to control the spread. The dye will limit the amount of sunlight that reaches the pond bottom; thereby making it difficult for the Lyngbya to become established. In ponds with low water movement, a surface fountain or aerator can be very beneficial. Reducing available nutrients in the pond with commercial binding agents like Phoslock is another option. And finally, routine algaecide applications help keep the growth in check. But in the end, there is no simple solution for permanent removal. The good news is that Lyngbya is usually a temporary problem. It flushes out of the pond with heavy rains, and it will decline in growth once water temperatures begin to cool in the fall.