Pond Boss Forums MANAGING AN EXISTING POND Fertilization Floating Scum Just Started....Why?

RLewis,
Yes it can negatively effect your pond.

You shouldn't be adding fert. by a date on the calender.
A pond is fertilized to maximize fish production.
Water clarity is the determining factor as when fertilizer is needed. You should try to maintain 18" to 24" visibility as measured with a secchi dish. Or use the aformentioned arm/elbow test.

If water clarity becomes less than 12" it is time to be concerned.
The green color is from phytoplankton. Phytoplankton produces oxygen during a sunlit day & consumes oxygen during the night or on cloudy days. When you have too much bloom ie less than 12" vis. it is very possible to have a DO (disolved oxygen) crash & loose fish.
This normally occurs early in the AM when the over abundent plankton has used all the DO just trying to get through the night. The plankton dies & more oxygen is used as it decomposes.

If I were fertilizing I would not add any more until vis. was >= 24".