Many ponds on a variety of soil types are prone to water loss by seepage. This water loss can be controlled by the application of western sodium bentonite clay. Sodium bentonite is a naturally occurring clay which contains no additives.
 
Sodium bentonite clay swells up to 12 times its dry size when it becomes wet. Bentonite is environmentally safe and does not affect the water, livestock or wildlife. When properly applied it will not harm fish. Bentonite is easily applied. In the case of small ponds, it can be applied with simple hand tools and, for larger ponds, with ordinary farm equipment.

Blanket method

The blanket method can be used in new pond construction and in existing ponds that can be drained. This is usually the most effective method to control water loss. However, more care is required during the application process.

Bentonite deposits are normally exploited by quarrying. Extracted bentonite is distinctly solid, even with a high moisture content of approximately 30%. The material is initially crushed and, if necessary, activated with the addition of soda ash (Na2CO3). Bentonite is subsequently dried (air and/or forced drying) to reach the moisture content of approximately 15%.

According to the final application, bentonite is either sieved (granular form) or milled (into powder and superfine powder form). For special applications, bentonite is purified by removing the associated gangue minerals, or treated with acids to produce acid activated bentonite (bleaching earths), or treated with organics to produce organoclays.