Recently I posted a question regarding scum on the surface of my tank....no
answers yet but I have new evidence...

I have left it for a whole weekend - when I got back the surface was covered
with a fine green dust. It had bubbles on it which resembled a scum or froth
of sorts. When I dipped my finger in, the scum closed around it, when
retracted there was no evidence that I had distured the surface. It left a
very fine green film on my finger which resembled dust and rubbed off
between my fingers - it looked like powder and not blue-green algae. It's
the sort of scum that you find on stagnant ponds or water that has been left
for an awful long time.

Does anyone know what it is....

I have just put my venturi jet back on and directed it at the surface...
The Chemistry of the tank is fine everything 0 or normal. I do use CO2
injection, I perhaps do not have the amount of plants I would like to have
at the moment. Light is ot too strong 2x20W tritons and 1x30W flora glo.
Filter is Ehein turning over 660lph on a 250l tank.
I have just been rearranging the outlet once again to try and get as much
free floating rubish out as possible.

I do have riccia fluitans on the surface and some ceratophylim demersum -
these have both been removed now as I am thinking on the lines that the
surface plants are producing spores which are then breeding ???

Any suggesstions would be a great help.

Thanks
Martin