Yeah, that spot did not get much flow at all. I bought a small powerhead, there is more flow now. It' can't be too much since otherwise my borellii are just flying around. I got it mainly for my sewellia, he seems much happier now. Also added some stones for him.
I think the wood is mongrove.
I got Easy Life Blue Exit, which I started dosing now for the BGA. I don't even know what is contains (which makes it pretty dangerous to use), but many had had success with it so I'll try it out. I also heard that hydrogen peroxide will demolish BGA, but that also demolishes all the beneficial bacteria so I decided to skip on that. Btw I can just scrape it off or even remove it in sheets or pieces, it comes off very easily.