Hi Biggles!
ZeoSpur2 is an alguicide. It does kill zooxanthela (Symbidinium) and also some dinoflagellates at higher doses. As Sahin says, be careful in the long run as it tends to thin up corals tissues.
I'll tell you how to use it:
Do not pour the stuff in the tank, just make a 1:10 dissolution (ZSP2:tank water) and dip the brown turd you want to clean up from zooxanthela for about 1 minute. Then put it back in the tank and wait 24 hours, the change it makes is awesome.
Only do it with healthy and browned out acros, never dip a just bought or recent frag as you can easily kill it.