What is this stuff?

[redburn]

Hello everyone.
What is this and is it bad? It seems to be popping up in several spots in my tank. This is the largest and seems to grow rather quickly.
Thanks

 

[griss]

Looks like a sponge or sea squirt to me. Both are harmless and beneficial filter feeders.

 

[Guygettnby]

It's an alien! Better nuke it before it tries to take over your brain!

Seriously though, I agree that it looks like a sea squirt. As your tank matures, you will find tons of them hidden in your sump or filtration areas.

 

[ngocnhungplaza]

Looks like a type of turf algae or possibly Bryopsis, but it's hard to say for sure without a closer pic. If it's growing fast and spreading, you might want to manually remove it and keep an eye on your nutrient levels (nitrate/phosphate). Check your flow and lighting too—sometimes those can contribute to outbreaks. Definitely don’t ignore it though, it can get out of control pretty fast.

 

[Reefing102]

Looks like a type of turf algae or possibly Bryopsis, but it's hard to say for sure without a closer pic. If it's growing fast and spreading, you might want to manually remove it and keep an eye on your nutrient levels (nitrate/phosphate). Check your flow and lighting too—sometimes those can contribute to outbreaks. Definitely don’t ignore it though, it can get out of control pretty fast.

Not sure what you’re looking at in the pic? But the white is definitely a sponge or sea squirt.