What are these white/clear things

[Izzy’sReefTank]

What are these? They are on my undersides of my rock work and in my sump so I know they don’t like light?

 

[laezur]

Look like sponges to me, harmless filter feeders.

 

[ISpeakForTheSeas]

Pineapple sponges (genus Sycon) - they're common in new tanks and typically boom then bust in population and go away on their own. They're harmless filter feeders.

 

[Tired]

Yep, pineapple sponges.

 

[Izzy’sReefTank]

Thanks everyone my tank is almost a year old now, so was just making sure I didn’t have an issue that was going to harm it.