[Achilles]

I absolutely agree with Dave on his explanation of how to treat the cause. To limit the look of the algae in the mean time. Syphon as much as you can off, and cut your photoperiod down while you start to dose the kalkwasser at night. The limited photoperiod will slow it's growth, while you hit it below the belt with the high alkalinity etc.

something to note, if you have this algae in abundance, you have a nutrient imbalance. You must treat the symtoms.

Check to see that the aquarium is not recieving too much sunlight. If so, cover up the tank when it's designated photoperiod is not in progress.

The same methods Dave and I describe can be used to fight dinoflagellates if you ever have them.

Cheers!

Jeff O'Neill