Native Plants

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Sunday - December 16, 2007

From: Rockledge, FL
Region: Southeast
Topic: Problem Plants
Title: Prevention of algae scum on standing water
Answered by: Barbara Medford

QUESTION:

Because your answer to a previous question has resolved an "issue" referent to proper care of our cordgrass plants, I'm back to ask your advice. The pond behind our condominium complex is man-made and is not spring-fed. It's "standing-water" content comes from area rainfall that is funneled into the pond. Over the past several months, the top of the pond has developed patches of "scum" (algae growth) that moves across its surface depending on the direction of the wind. It is somewhat unsightly and residents have asked if it could be removed. We have have been told by area businesses that we could clear it out, but it might result in increased algae growth. To be blunt, it's pretty nasty looking. Can we/should we remove it? Again, thanks for your previous help. It was sincerely appreciated by all concerned.

ANSWER:

Just to bring everyone up to speed on the cordgrass issue, please refer to this previous Mr. Smarty Plants answer. Your standing water problem does not stem from the cordgrass, but we're flattered that you came back to us with another question on the landscape management of your condominium complex.

If we understand you correctly, the water area in question is basically a retention pond, and not intended as a scenic feature of the property. This website on Retention Pond Facts, originating from several organizations in Florida, gives some information on their purposes and problems. These ponds are designed to address the increase of development in an area creating more impervious areas; i.e., paving, parking lots, driveways, and buildings, where storm runoff cannot readily soak into the soil. The retention pond traps some of this runoff, preventing further flooding downstream. It also traps pollutants such as excess lawn and garden fertilizer, pesticides, animal waste and motor oil, helping to protect the quality of water in natural waterways downstream.

The bad news is that the water is just sitting there in the pond, with all of that bad stuff in it. Sometimes oxygen is introduced into water in this sort of situation by waves, wind or other means of mixing some oxygen in for aerobic decomposition of the waste materials in the pond. If oxygen is not being introduced, the decomposition becomes anaerobic, resulting in unpleasant odors and, yes, algae bloom.

Having looked at all these facts, it would appear that a good alternative would be an artificial aeration system. Since this is a little out of the realm of our expertise at the Lady Bird Johnson Wildflower Center in native plants of North America, we would recommend you follow this up with more research of your own, determining what is economically practical and most efficient.