Algae is not harmful, but unsightly. You should use algae as an indicator to determine conditions in your pond.

While crystal clear blue water is nice in your neighbors spa or swimming pool, it is not conducive to ponds or fish. All ponds should have a nice coating of algae on the sides, indicating a healthy environment.

Free floating or hair algae, which causes the pea soup effect is not desired. This means you do not have sufficient coverage on your water surface or enough oxygenating grasses. Coverage is obtained from waterlilies or other floating aquatic plants. On a Koi pond you may need a U.V. sterilizer.

You should have 65% of your surface area covered and no more. Too much coverage will not allow the pond to breathe. If you pond is a naturally balanced pond, the algae could indicate an insufficient amount of submerged oxygenating plants.

The oxygenating plants compete for the same sunlight and nutrients as the algae and eventually starve the algae, resulting in clear water.

Using a liquid type fertilizer that is poured directly into the pond water will cause a bloom of algae - use a tablet type pressed into the soil of your potted lilies and aquatic plants.