Question
I have a small pond with a water fall (the pond is 5'x8'x3'deep, with a small water fall chamber above it. The water is fairly clear (not crystal though)and at the waterfall and around the edges  a whitish foam will appear.Also there is lots of green stringy stuff growing from the large river stones inside the pond and I cannot see the bottom. It is completely shaded by a large ash tree in the summer, and I have seen this green stuff only come out since the leaves have been gone from the tree, Can you tell me what kind of algae this is and what to do about it? Also what about the whitish foam ? My pump has a UV sterilizer in it and is circulating the water well. I have 3 comet goldfish about 5" long & three of the calico goldfish about the same size in there too. Any help would be appreciated and thank you !

Answer
It is called string algae. A real challenge to get rid of. No algae until the leaves fell off  the tree indicates more sunlight and not too many plants in the pond. The foam indicates an excess of phosphate. An algacide might help it will gwt some of the algae to the surface so you can skim it. To get rid of the algae from the rocks you will probably have to scrub them. Try unplugging th UV filter for a few day sometimes ponds need some good bacteria to fight the bad.

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