Many filamentous algae, including green and bluegreen, float atop the
water, for various reasons. Death of the algae is not the most common
cause. More often, oxygen bubbles (produced by photosynthesis)
trapped in subsurface mats lends buoyancy, which is frequently
substantial enough to break mats from substrates and result in the
floating messes everyone seems to be so fond to find in their ponds.
If the floating mat is bright green, it is likely a green algae, such
as Spirogyra or Mougeotia. If it is dark green, it is most likely a
bluegreen algae, such as Lyngbya or Anabaena. If it is brown, it is
probably dead, and carbon dioxide, not oxygen, is causing flotation.


"Chris Tondreau" wrote:

Thank you, yes that is what it appears to be, not the nice harmless duckweed
as the other poster suggested. Drat!! Will do some more research on
methods to get rid of the stuff & revitalize the pond.

Jacqui

"K30a" wrote in message
...

I did a search for floating mats of algae and came up with blue-green
algae
over and over. I suggest you look in that direction.


k30a