It is black algae, I can scrape them and it is dark green, it looks tar-like when it is at the bottom and has tough texture and if I remove with a bit of force (from where I can) they float and are like algae. As I said in my previous post I was able to remove a lot of it using the wirebrush, and they were caught in the secondary skimmer (fine mesh) and they are green, granular and plant like. but it got to a point where it doesnt go away at all after 3-4 weeks.
I will use trichlor and let you know how that goes. I have trichlor tabs, but the problem is I dont know how to apply directly on top of them especially the walls. If I get the granules I can sprinke at the bottom to see if it makes a difference atleast at the bottom so I will know it works.