In alt.aquaria NetMax wrote:
Does anyone have any experience with this? It's like a very fine
grey-green powder floating on the water surface. It appears quite dense,
making very interesting patterns (grey-green swirls) when pushed by the
filter output. If I touch my finger to the surface, it immediately pulls
away leaving a clearing about 4" in diameter, so it's not very thick.

I'm not necessarily looking for a way to get rid of it as most of these
funky algaes come & go without any intervention from me, but I was trying
to collect some info, as I haven't seen this stuff mentioned before. TIA

I have something akin to that on some of my tanks. It seems to only
develop around floating leaves or protein films in my tanks and even
strong surface agitation only moderately deters it. I swear we get every
kind of algae problem here locally because of the fertilizer runoff in the
tap water. I think it might be a kind of cyanobacteria. In my tanks where
it has something to latch onto on the surface, like floating leaves, if
left unremoved, it will grow into something akin to pond scum. Slimey,
lots of air bubbles with a yellow-green color. I get it most often in the
back of my 30 breeder among the floating val leaves because it's a bit
harder to see that far back into the tank with the stand its in so I
usually don't notice it until it starts cutting the light back a bit. Just
pulled a bunch of it out of that tank last night actually. Very strong
smelling too.