Happy'Cam'per wrote:

They are indeed photosynthesising, why are they green??

While Cyanobacteria can photosynthesize, that is not it's only source
for nutrients. It is not a plant - it is a bacteria. Unlike 'regular'
algae, it is not dependent upon ammonia related products (including
nitrite and nitrate), and can directly process molecular nitrogen.

Since it isn't dependent upon photosynthesis, a blackout may stunt it
but won't kill it - it can employ other food sources.

You would feel much more accomplished if you defeated the beast
without the aid of antibiotics! Do deep gravel cleanings and clean
out your filter thoroughly, 70-80% waterchange.

I'm not seeking a sense of accomplishment, I'm just trying to get rid
of the BGA. I've done *loads* of gravel cleanings, scrubbing, water
changes, and filter changes. In my experience, as long as the
conditions in the tank support BGA, any cells that escape the cleaning
will spawn the problem over again.

--
Eric Schreiber
www.ericschreiber.com