BGA thrives with low oxygen and high organic wastes. So maybe your mystery algae does, too.
All the pictures in this thread appear to be from tanks lightly planted with slow growers, which supports the possibility of low oxygen/high organic waste conditions.
The lack of BGA in your tanks doesn't mean these conditions don't exist. BGA doesn't just spontaneously appear, it must be introduced. Once you have it, it can be eliminated completely; never to appear again until reintroduced, even if conditions are perfect..
I don't think this came from low oxygen? I have a 1100gph pump with a Mazzie, When I'm not pumping co2 in at night I got a lot of flow movement in my tank.
Will it looks to me that my algae battle is over now , My Dc is still the same transparent blue,I added more Fe, an I have 2 pair's of t5 54w 6hr's a day , I'm also keeping my co2 bubble count to 3bps, I don't know if my Nu-Clear 547 cycle that did it or my other settings but gravel has been clean of algae since last week tooth brush cleaning .
My sword and 5 stem plants are growing bigger now , I still need to add more.
I don't think this came from low oxygen I have a 1100gph pump with a Mazzie when I'm not pumping co2 in at night I got a lot of flow movement in my tank for a 60x18x24 tank.
My algae started in the center on the gravel not on plants or glass , Toward the end of the algae cycle it spread more to left side of my tank where I have 4 small plants, On the other side it did not reach I have a large sword and 5 stems growing real good. I still need to add a lot more plants in my tank.
IMO: My BIO Filter was not cycle yet and low on ferts , The only test kit I have is for KH, an PH , I do need to get PO4 , an KNO3 test kits