In South Carolina, where many of our ponds have been constructed in clay soils, pond water quality may be less than ideal for fish management. Liming can be an important step in a productive and healthy fish pond as lime can improve pH, hardness, and alkalinity conditions, all important factors in fish health. For highly-fished, low-flow ponds where fertilization may be needed to support a beneficial phytoplankton community, liming may be required for effective fertilizer applications. (Contact your local Extension agent to find out more information on pond fertilization and if it is appropriate for your pond.)
Are you wondering if you need to apply lime? This fall is a good time to find out. Collect and submit a Pond Bottom sample, a type of soil test, for analysis to the Clemson University Agricultural Service Lab. To collect your sample, you can rig up a long PVC pipe with a can attached to the end to collect 8-10 pond bottom samples around your pond. Check out Water Resource Extension Agent Susan Lunt’s DIY assembly she used to assist a homeowner at their pond in the Upstate. Once samples are collected, combine, dry, and then prepare a pint-sized mixed sample to be sent off to the lab. And, don’t forget to submit your accompanying Soil Analysis form, with “Pond Bottom” selected! Contact your county Extension office for more information on submittal. Once processed, you will receive results from the laboratory on pond bottom pH and lime application recommendation in pounds per acre.
Fall and winter are the best time of year to apply lime to your pond. If lime is needed, look for dolomitic (CaMg(CO3)2) or calcitic (CaCO3) lime sources. Avoid other forms of lime that may pose toxicity issues to aquatic life. When applying lime to your pond, the goal is to lime the pond bottom. This is best done when your pond is dry. However, if your pond is full, lime can be evenly scattered across the entire surface of the pond instead.
For more information on liming ponds, review the HGIC 1711, Liming Recreational Ponds.