Is this a purple sponge? Or something else....good or bad?

[clhardy5]

This purple stuff is starting to spread in my tank. Kind of looks like a sponge, and is soft/mushy to the touch. Doesn't seem to be irritating anything yet....but if it's a problem, I would love to head it off! Ideas?

Tank is 9 months old:
Current parameters:
Alk 8.5 (trident)
Calc: 435 (trident)
Mag: 1423 (trident)
Nitrate 13.4 (Hanna HR)
Phos: .03 (Hanna LR)
Salinity 35ppt
PH: 8.2

 

[blaxsun]

Someone finally got Barney!

 

[Isopod80]

Yup, it's sponge. I've had the same variety in my tank for some time now. Appears to be a slower grower compared to most sponge varieties. Harmless filter feeder but I'd scrub off what you don't want with a toothbrush if it grows too close to corals. I've always done this during water changes so I can siphon out the unwanted sections as I'm scrubbing.