Clearing the water in a hurry, whether for a party or to enhance mechanical filtration, can be done using a flocculent. It is a liquid that is added to the pond, doing its' work in a few hours. The material, sold under the name of Accu-Clear, causes suspended particles in the water to stick together. This makes the larger particle heavy, causing it to settle to the bottom of the pond. When using a mechanical filter, these heavier particles can be removed from the water easily. This product should not be used as a substitute for healthy, balanced water. It does not kill the algae, it only makes it drop to the bottom of the pond. In a few days the water will again be green unless the algae is killed or filtered out.