These "Jelly Balls" are a primitive colonial invertebrate known as bryozoa (common name is moss animals). They are firm and slimy to the touch and can range from golf ball to basketball size. They are not fish or frog eggs, a form of algae or lake bacteria.
Even though they appear to be something out of a science fiction movie or from outer space, they are completely harmless to you and your pond. Where do they come from? Most commonly, they attach to animals that travel from one pond to another.
They are filter feeders that sieve food particles out of the water using retractable tentacles. Fresh water bryozoa feed on many varieties of algae including diatoms and Planktonic Algae, keeping water clean. They are not an indication of water pollution. They seem to prefer a highly-organic pond bottom and are a useful indicator of water quality.
"Jelly Balls" are occasionally a nuisance in water pipes, drinking water purification equipment, sewage treatment facilities and cooling pipes in power stations.
Physical removal is the only known way to clean your pond of "Jelly Balls". They are preyed on by snails, insects and fish. No aquatic herbicide will affect these
gelatinous balls. But, do not fear, if you do nothing they will begin to disappear in the late fall when water temperature drops to 61 degrees F.
Please feel free to email me or post questions you may have and I will respond accordingly.
FarmingForWildlife.com, "Jelly Balls" What are those things in my pond? Don Keller/Barry Smith
Marks Outdoors Sports, Moss Animals by Graves Lovell
Bryozoa - wikipedia,the free encyclopedia