I would like to share a good experience with everybody of this groups. For a
couple of months I fought a battle against the so called Green Dust Algae.
The growth of this harmless (?) but annoying algae was so quick that I had
to wipe the screens every other day. Sometimes, the algae reappeared within
a few hours after cleaning. Approximately one month ago, I found an older
thread where Tom Barr claimed that he knew how to get rid off these algae.
He stated that you have to keep your hands away from the screens for about
three weeks, then the algae would get into a different stage of their
life-cycle and finally die off. I was a bit sceptical but I tried this
method. After two weeks, the glasses looked already a bit different because
some algae eaters (they have been in the tank from the beginning) had
already cleaned some part. They must be more careful than a human hand with
a scrubber than it seemed that no new algae grew on the tracks of the
cleaning crew (SAE and neritina snails). I waited two more weeks, the tank
looked not bad. Then I reactivated the srubber and cleaned the last patches
of GDA. Surprise, surprise, the screens remained blank. How long this state
will last, I don't know. But I think it is a good idea to try the method
yourself if you have the same kind of problem.

I put a question mark behind the word "harmless" because I sometimes
experienced a pretty strong smell when I cleaned the screens in the past.
The smell was like ozone or nitrous oxide fumes. Therefore, I am not sure
wheteher GDA can release toxic substances.

Juergen Beisser