Can U Help Identify These?

[three-fingers]

Dis some research, they are sponges in the family Sycettidae, presumably in the genus Sycon, as the ones in our aquariums are usually just referred to as "Sycon sponges".

So totally harmless, potentially beneficial filter feeders .

 

[SkiFletch]

Wow, one heck of a lense you used to take those shots. Most sponges are great beneficial organisms. I'd be curious if their population waxes and wanes over time of if they have a steady enough food supply to live