Black Algae?

[Andrew_B]

I haven't noticed it until I was recently playing around with bulb spectrum's on my tank, but apparently my black volcanic rock is slowly getting a thin coat of what looks to be a black/dark colored algae. It seems like each of my tanks have are different in terms of algae. One tank doesn't get any, another has green, another has brown, and this one has black. Each of my tanks have different lighting in them.




Does the bulb spectrum determine the amount/kind of algae that grows? None of the tanks have any big outbursts... they seem to stay in check with BN plecos, but should I worry about taking action about either of the algaes, mainly the black?

Thanks