Hi Guys,
I got Black Spot Algae recently and seems spreading out.
After I changed to use Tropica Plant Nutrition Liquid, BSA appeared.
Anyone here knows what does it causes?
And someone here can probably point me how to get rid this algae?

I'm not sure what black spot algae is, unless it is black brush algae, the only black looking algae I know about. If that is what you have, it seems to show up when the CO2 is either inconsistent or is just too low, and the light intensity is high.

I am proud to say I am very, very good at growing black brush algae. I'm thinking of an aquascape built around this beautiful algae. (Maybe if I can convince myself that I want it, it will go away.)

Thanks VaughnH.
Fixed. It is a early stage of GSA.