What is this algae? dinoflagge? - What to kill this sucker?

[Guys and Gals,

A while back I posted an algae outbreak in my brother's tank. The liverocks were nicely covered with coralline algae. Since the algae happened, it has covered all areas of liverock that contact the light. Any area of liverock where the light doesn't reach to still has nice purple coralline. This algae has no bubble and doesn't look like it can come out easy. I went to Dallas North Aquarium and saw one tank has the same problem, a redish brownish algae cover the liverock. Nothing died in the tank but just make things look so unattractive. I tested all parameters and Alkalinity was low and I got it back in range already. Can you help?]
 
[Can you siphon it off easily. With out more into I vote Cryo bacteria. Is it appearing in low flow areas of the tank, parts ogf it grow into the sand?]
 
Top