I have a 26g fully planted tank. Phosphate readings of my tap water
is .25-.5 ppm. My tank registers close to 2.0 I do weekly water
changes(25%), clean exposed gravel and feed the fish once daily.
Lighting is 55w on for about 10-12 hours/day. I use fertilizer once a
week, potassium twice weekly and have a diy CO2.

I think I should be lowering the PO4. Some algae buildup is showing
on my plants. Other than more water changes should I be using
something I saw at my LFS. It was a white sack with some type of
granules in it. Claims to reduce PO4 and is good for 3 montshs. Put
in filter or in tank. Is this charcoal? I've heard people using
this but never knew for what purpose. I don't have room IN my filter
so would have to slip it into the back of my tank behind plants.

Your advice?
(also posted to rec.aquaria.freshwater,misc.)

Larry