Black algae - need help with identification

[Marcel G]

Hi, my friend have some black algae in his tank. He has it on the Echinodorus leaves, on Vallisneria and some other plants. Also the algae is on some equipment (spray bar + in the corners of the tank). It seems to me that it could be related to a too-low-light problem. He fertilizes according to Estimative Index, and uses pressurized CO2. He changes 50% of water each week also.

Please, can you help me identify this kind of algae (see photos) and what could be the possible cause of it?

My friend's tank specifications:
Tank volume: 30G
Light: 2x30W T8 (Philips Master bulbs)
PAR: 20-25 umol (at the substrate), 50 umol (middle), 120 umol (just under the the water surface)

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[niru]

Hello Kwisatz

I too have this same algae, and Tom suggested its GDA, turned black. It seems its related to CO2 issues. I have recently tried to fix this CO2 distribution, and am waiting for results.. Cant help much on this, but am interested in any replies to your question.

cheers
niru