What are these?

[Paisley Rain]

Can anyone identify what these little critters are that were hiding in my filter media? Assuming a species of nudibranch? I had put two berghias in the tank months ago to try and get on top of an aiptasia infestation, but haven’t seen them since and am losing hope. These guys don’t look like the berghias? I could be mistaken of course. Any help would be much appreciated!

 

[Gumbies R Us]

@ISpeakForTheSeas

 

[rayadog]

Color for me is throwing me off but they could be tiny bristleworms.

 

[SnappyShrimp]

Are they stationary? They sort of look like pineapple sponges, which would be a harmless filter feeder. They also seem to grow on my media bags after some time

 

[Paisley Rain]

Are they stationary? They sort of look like pineapple sponges, which would be a harmless filter feeder. They also seem to grow on my media bags after some time

After a moment of watching it looked like one lifted its “head” but I didn’t see very much movement from the others

 

[rayadog]

Are they stationary? They sort of look like pineapple sponges, which would be a harmless filter feeder. They also seem to grow on my media bags after some time

D’oh. Yea you’re right. That should’ve been obvious. Sorry.

It looks like you can clearly see spicules on one* that’s still in the cluster in the water, in the background.

 

[ISpeakForTheSeas]

@ISpeakForTheSeas

I'm late, but I second these likely being pineapple sponges (genus Sycon); they're common in newer tanks and tend to boom then bust in population before going away on their own. Harmless filter-feeders, and a lot of people consider them a sign of a healthy tank.