Hi franker! Please share images of the pond to have a look.
Have you done water test of the pond?
There may be imbalance in pond water ecosystem or it has high nutrient levels.
There are some products that are effective, Removed unauthorized advertising link to remove algae and hydra silt-less to clean sludge that make pond look murky.
Last edited by esshup; 08/01/14 09:34 AM.