yea you can use that extra tank, fill it 1/2 way with water. put your plants in, apply about 15-25ml of h202. directly to the leaves. let it sit for a while. then scrub off what you can from the leaves. you can keep them in this tank for a few days and repeat as necessary....a filter or anythign is not necessary just change out 1-2 gallons per day before application of h202.
you still need to find the root cause of your bba.
you still need to find the root cause of your bba.