Blue-green algae can occur in almost any body of water, but are particularly common in ponds and small lakes. Not only does it produce an ugly film on the water's surface, but blue-green algae can also cause health problems to life in the water as well as anybody who comes in contact with it. According to the Wisconsin Department of Natural Resources, the best way to control blue-green algae is through natural measures, but it can take several years to get rid of it completely.
Refrain from the use of lawn fertilisers unless you absolutely need to. The nutrients from lawn fertiliser can leak into the pond or small lake and increase the amount of blue-green algae it contains.
Keep the grass, shrubs and any other plant life near the water and storm drains trimmed and clean. Do not let clippings from any plant life build up in these areas as it can encourage blue-green algae growth.
Plant shrubs along the shoreline of the water to prevent fertiliser runoff from entering the water. Do your best to use plants native to the area as they'll grow stronger root systems which can block runoff more effectively.
Do not use chemicals to treat blue-green algae as they might pollute the water and harm lifeforms living in it.