I would skip gravel vac'ing. You're pulling up fish poop which is good food for your plants.
Other than that - consistent water changes are always a good thing.
Algae wouldn't move the second you put your hand near it, imo. All the clues make it seem like mulm.
Mulm is a good thing for your aquarium. If you don't like the look of it, then gravel vac is the easiest way to remove it.
Do you have a link for this?
Sorry...thread from the dead...but looking into a store bought option. Hand grinding in a plastic container is a lot of work.
A quick update on this.
I went with the alternative Co-Op website recommendation of trimming it, and planting it as a 'bunch'. Added an airstone to the tank, and....poof! THRIVING
It's definitely a bucket list place to visit for myself.
My wife has a work conference in Seattle next year. Hoping that she can go. If that happens, I'm getting to the store someway somehow.
This is incredible. Your vision. Your detail. This is everything a biotope should be. Well done! Very original. I've never seen a setup like this before. Be proud!