If you're getting a lot of algae on your pond, that means something is happening upstream. Homes with septic systems or sewage treatment plants are the primary suspects.
Chemicals can be used to control algae, but contact your local Extension or NRCS office for information on using them properly.
"Those offices will know which type of chemicals are needed and can recommend approved treatments for your area," Loser says. "Certain chemicals may have permitting requirements. It's critical to calculate the amount of water in the pond accurately so that you don't cause additional problems."
|Don't let natural water sources scare you unnecessarily||
For the more motivated and environmentally conscious, algae can simply be raked off.
There are other concerns about horses drinking from natural sources.
Horses drinking from marshy areas or areas where wildlife or cattle have access have an increased incidence of moonblindess, Larry Lawrence points out. Even mountain streams can have sand beds, and horses drinking might ingest enough sand, over time, to cause colic.
Fresh water snails have been identified as a carrier of the agent causing Potomac Horse Fever.
But don't necessarily let the thought of natural water sources scare you. "The Council for Agricultural Science and Technology reports very few toxicities to livestock from ingestion of natural constituents in drinking water," says Lawrence, an animal scientist with Virginia Tech. "Just be conscious of rapid changes in water sources because horses are sensitive to unusual tastes and odors."
Check your horse's water bucket and trough every day to make sure the water is clean and plentiful. "Restricting a horse from water for as little as two hours significantly increases the chances of colic," Lawrence warns.