red coralline

Does anyone have any theories as to what causes the proliferation of "red coralline"? I believe the species isn't actually a part of the coralline family but rather a red thalloid algae from the genus Peyssonnelia sp. or maybe Hildenbrandia rubra. Some systems appear to have none, whilst others...

Up until a little over a year ago, I always assumed all the hard, red encrusting algae we find in our marine tanks was just another variant of Coralline algae. Boy was I wrong! I eventually came across this site which made me realize that this "red Coralline" might actually be of the genus...