Don't know if a pleco will eat it. My otos don't touch it. I think my RCS pick at it a little, but they don't really make a dent. My wife's mystery snail seems to like it.
I have no idea about silicates or phosphates. I haven't tested my water for either. I do know that I only get that kind of algae in my higher light tanks. I suspect that it is an imbalance of certain nutrients, but I haven't really tried to figure out which ones are off. It seems to have receded since I switched from the bargain bin ferts to Flourish.