[Ebichua]

Looks like black beard to me as well. Directly spraying the plants with excel will usually kill this. Increase the co2 in the tank as well.
Black-outs for 3 or so days is also another option.

 

[Ebichua]

Different algae grow in different conditions. Some green spot is normal, having GSA growing too much on the other hand is not. Too much green spot algae means the light is on for too long. I also recently learned that it's also a cause of low phosphates.