Pond Renovation

Introduction   |   What is Rotenone?   |   Preparing the Pond   |    Applying Rotenone   |   Restocking the Pond   |   Toxicity and Neutralization   |   Partial Fish Kill   |  

Click here for a printable version of this publication: Using Rotenone To Renovate Fish Populations In Farm Ponds

Applying Rotenone

Ponds of any size can be treated with rotenone, but it can be difficult to achieve an even distribution of rotenone for an effective fish kill in larger ponds or lakes. It is also expensive to treat large volumes of water. For these two reasons, it is advisable to reduce the water area and volume as much as possible before treating. This can be accomplished by draining the pond as low as possible with a built-in standpipe, by a pump, or by a siphon device. The less water you treat, the more cost-effective the treatment.

A simple siphon can be constructed to drain any pond where the ground level behind the dam is lower than the water level inside the pond. This device is constructed of PVC sewer pipe and duct tape. A diameter of 3 inches is easiest to handle, but larger diameters drain the pond more quickly. Two or more drain pipes can be used to decrease draining time. The technique is simple. Glue or tape several joints of pipe together, and install a female adaptor and male clean-out plug on one end. On the opposite end of the pipe, tie a gallon jug onto a 12-to 18-inch string attached to the pipe, then tie a 1/2- to 1-pound weight to the pipe. Locate the pipe in the center of the dam or levee, or at the point where the ground level behind the dam is lowest. Push the pipe assembly into the pond (float and weight end first) perpendicular to the dam. The weight will suspend the suction end about 12 to 18 inches below the float at the surface. Remove the plug from the near end. Allow the pipe to fill completely with pond water. When the pipe is filled, insert the clean-out plug to seal the water inside the pipe. Pick up the plug end of the pipe and carry up and over the dam to the back side at the lowest point (be sure the pipe assembly is long enough). Once the plug end is at the lowest point behind the dam, unscrew the plug and allow water to flow out, creating a siphon that will drain the pond to the level of the outside end of the pipe. If you have made good, airtight connections, the siphon will flow smoothly and continuously, until the water in the pond is lowered to the level of the outlet on the back side of the dam.

The best time to eradicate fish from a pond for restocking is late summer or early fall. Water temperatures are at their highest at this time, and the weather is usually dry, allowing easy draining. Killing the fish at this time reduces the time between the kill and the restocking, which minimizes the chance the pond will be contaminated by unwanted fish before restocking. This is an important consideration, since the entry of unwanted species can defeat the purpose for the renovation.

Treatment rates will range from 0.5 to 3.0 parts per million, depending upon the species being killed.

If there are any puddles or pools in the upper portion of the pond after draining, it is critical that these also be treated to kill any fish therein. Many small fish can survive in these pools, puddles, or stump holes for long periods. These must be killed to accomplish a successful renovation. Otherwise, these surviving fish can represent contamination of the new fish population, and the renovation will have been for nothing.

If rotenone is washed out or otherwise escapes the pond and enters any other body of water, it can kill fish. This is a danger of rotenone application, and it is against label recommendations to apply rotenone in situations where it can enter nontarget waters. However, the rapid breakdown of rotenone minimizes the likelihood of toxic effects downstream if applied properly in a drained pond.