Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Getting rid of BGA:
Turn off your filter(s), lower your water level, and dose hydrogen peroxide (h2O2), at close range, using a syringe or test kit pipette, over all the affected areas. Leave the filters off for about an hour, so there is no water flow to remove the hp from the affected areas. You should soon see it getting covered in bubbles, and the bubbles popping up into the water column - a sign it's working.
Refill your tank, turn your filter back on, and leave it overnite. Repeat the procedure the next day, if there is still some BGA remaining.
Cause - and remedy for preventing it from coming back:
Possible very low level of nitrates, accumulation of decomposing plant matter & food, etc., dead spots in the tank and lack of circulation and oxygenation.
Clean/vac the substrate well, and up the water circulation and oxygenation throughout the lower levels of the tank. A water circulation pump is best, but stronger filtration, or a spray bar, a powerhead, & an airstone may be sufficient to do the job. And possibly increase the nitrates level somewhat.