I have to agree that in general where plants grow readily algae is sufficiently reduced; though I still do regular bi-weekly water changes. I don't have pearlweed; not even sure what it looks like but I do have other fast growing plants like hornworth and italia val; they require regular weekly pruning do to aggressive growth.Also- you wont read elsewhere? I've noticed since it (pearlweed)became a sizeable plant? I am able to stretch water changes and the aquariums other plants look much better than in my once a week routine I had. I can't print out stats..just observations I'm seeing much less black algae.brush and the stuff that looks like black spray paint on Anubias. Every other week or so..if longer fine, is the new routine.
It and Cryptocoryne balansae are looking lush and real competition for bad algae.