Fish will act skittish anytime there is something
out of the ordinary for them.

That would be - netting out unwanted fish,
an attack by a predator (heron, raccoon, snake,
kingfisher), something falling into the pond, basically
anything that disturbs their world.

Sounds like the water was murky and now clearing
up. They are probably feeling vunerable from the surface.

Cleaning the pond will be traumatic, no way around it
but not cleaning it could be worse.
Also I would not clean the algae off the sides, substrate
algae like that is part of the pond's natural balance.

kathy :-)
www.blogfromthebog.com
new entry ~ herons