For pond owners, there is nothing more relaxing or satisfying than to catch a few fish on a warm summer evening. This year, however, many Georgia ponds have turned a yucky shade of brown that isn't going to make you want to do much fishing.
This brown material seen in many ponds this time of year is a brown phytoplankton bloom. We have it every year, but some years are worse than others.
Phytoplankton consists of tiny, almost microscopic plants that float in the water and comprise the bottom of the food chain in a typical pond. These phytoplankton are usually green, and a mass, or bloom, gives a pond its normal green color.
It seems to be worse in an early warm spring and early hot summer. A combination of weather conditions and certain micro-nutrients in the water probably trigger the brown phytoplankton blooms. The good news is that it is just as valuable a food source as the standard green plankton we normally see, and it tends to go away as the weather gets hotter and the sun gets brighter.
The only thing you need to be sure of is that it's brown phytoplankton and not a clay turbidity. While the brown phytoplankton is harmless and actually useful to the fish, clay particles in the water can cling to the fish's gills and greatly stress them. If it's bad enough over a long period of time, it can even suffocate them.
Clay turbidity and a brown phytoplankton bloom may look much alike at first glance, but they're easy to tell apart. The first giveaway is whether there's disturbed soil in the watershed. You can also just look closely at the water.
Looking at the water under a magnifying glass will reveal the shapes of the particles floating in the water. Phytoplankton will have regular shapes, such as ovals and rectangles. Clay particles, though, will be rough, rocky, irregular shapes.
Clay particles can take on negative charges and repel each other, which tends to keep them suspended in the water. Applying lime can take away those negative charges and allow the clay to settle out.
If clay turbidity is a problem, you need to take steps to prevent it by stabilizing the soil where it is washing into the pond, or change the access point for any livestock entering the pond.
If the problem is a brown phytoplankton bloom, it's not really a problem. Keep up your regular regimen of fertilizing the pond, and it's likely to turn green again before you know it.
For more information on ponds, check out the UGA Extension Aquaculture publications on line at www.ces.uga.edu/pubs/pubsubj.html#Forest
Billy Skaggs
Agricultural Agent Hall County Extension Coordinator
734 East Crescent Drive
Gainesville, GA 30501
Phone: (770)531-6988 Fax: (770)531-3994
Email: [email protected]
Sunday
August 10th, 2025
6:00AM
