Fuzzy growth on Waterfalls, Rocks and Pond sides

A little bit of green fuzz on the sides of the pond does not hurt anything. It makes it more natural and gives the fish a bit of healthy greenery to munch on.

If that greenery turns black and/or slimy though, then it is an indication of something that is not quite right in the pond.

It usually indicates that there is either not enough oxygen in the water or the pH is out of balance (or both).
The thing to do is test the pH and adjust it to within the safe range of 6.8 – 8.0 and make sure there is adequate oxygenation with a water feature (fountain, waterfall) or an air pump.

Existing growth can be cleaned off pretty easily with an oxygen based rock cleaner.