Purple encrusting something on rocks

[Kampo]

so I"ve had this thick purple growth on one of my rocks, its darker and more completly covering than the other coraline in my tank, and its now creeping accross the substrate. prolly 2-3 months to grow to the size it is now. any idea what it is? some sort of sponge I have read? should I remove? leave, honestly don't mind it, adds some color.

 

[Crabs McJones]

Can it be blown off with a turkey baster? Looks like slime algae or cyanobacteria.

 

[Kampo]

i've got some cyano elsewhere in the tank occationally looks different though more red. I did scrap it just now and it comes off resonably easy. maybe i'll just remove it next water change prolly something simlar to cyanobacteria really really slow growing though

 

[KJ]

Look like sponge.