How to Raise the Low Alkalinity of a Pond

Proper levels of alkalinity promote fish health.

A pond with low alkalinity usually has water that is clear or stained brown. Low alkalinity does not support the growth of algae that provide feed for the small animals that fish eat. A pond should have a minimum alkalinity of 20 mg/L, with an ideal range of 75 to 250 mg/L. With sufficient alkalinity levels, the pond water can withstand changes in pH better. You can raise the alkalinity of a pond by adding agricultural lime to the water.

Things You'll Need

• pH test kit
• Water container
• PVC pipe
• Liming material
• Shovel
• Liming truck
• Barge
• Lime spreader

Instructions

1. Take a pint of water from the surface of the pond and place it in a clean container. Don't include any mud or algae in the sample. Examine the total alkalinity level of the water sample using a swimming pool test kit. You need to raise the pond alkalinity if it is less than 20 mg/L.

2. Take samples of the sediment at the bottom of the pond to a depth of 6 inches with a piece of PVC pipe. Send the soil sample to a university laboratory or commercial testing center for analysis. Your local extension office can recommend some laboratories that provide such a service in your area. Soil testing determines the amount of liming material you need to apply to the water to increase the alkalinity.

3. Obtain enough liming material to raise the alkalinity of the pond according to the water and soil-test results. The University of Kentucky recommends using finely crushed agricultural limestone as a liming material. You can also use basic slag, slaked lime, quick lime or liquid lime.

4. Shovel the liming material into the surface of the pond evenly if your pond is 3 acres or smaller and you can reach every part of the pond. Alternatively, if your pond is less than 1 acre, back up a liming truck to the shore and use the truck lime spreader to apply the liming material. For best results, apply liming material in late fall or winter so the liming material has time to dissolve before the next algae growing season.

5. Place the liming material on a barge and shovel it into the pond if you have a large pond and can't reach the middle of the pond from the shore. Because of the amount of effort involved, you may want to use a special lime spreader machine to properly distribute the liming material from the barge. You can usually hire a professional pond consultant to do this for a fee.

Tips & Warnings

• You can achieve best results if your pond is dry when you apply the liming material. This way, you can use a liming truck to easily and evenly distribute the liming material all over the bottom of the pond.

• Avoid applying liming material during the growing season because the introduced material can remove nutrients from the water, making the environment less suitable for algae growth.

References

• Alabama Cooperative Extension System; Liming Fishponds; Russell A. Wright; May 2001
• University of Kentucky; Liming Ponds for Aquaculture; William A. Wurts et al