What in Tarnation is This?

[Seafeather]

Title says it all, honestly. What in the world is this thing? Ive seen it in my tank for quite some time and i just removed it from my big tank with more to lose, and into my tiny desk tank. I do know that a coral was on this specific rubble piece but i couldnt tell you what coral as it died off a while ago. There was always this thing there, but it got bigger and more bulbous. It looks like a purply steamed bao bun.

 

[KrisReef]

Second image looks like coralline algae on an old shell.

 

[BryanM]

My guess is it is a sponge

 

[Privateye]

I'd check it when the lights are off. It almost looks like polyps could come out of it. Basically, I'm wondering if it's a non-photosynthetic coral. I had some that looked just like that, but perhaps smaller. At night they'd put out red tentacles. The guy who collected it said it was a non-photosynthetic parazoanthus but I'm not 100% confident in that ID.

I also had a non-photosynthetic leather coral that would close like that...it was sold to me as an "anus coral" but I'm confident that's not the name! He just called it that because of how it looked when it was closed.

 

[Gone Reefin’]

Some kind of sea squirt? Anus coral is a fitting name looking at that thing!

 

[Seafeather]

Second image looks like coralline algae on an old shell.

LOL yes that definitely is. I was trying to get a top down image of the more bubbly looking thing in the corner of the tank, bottom of the image.

 

[Seafeather]

I'd check it when the lights are off. It almost looks like polyps could come out of it. Basically, I'm wondering if it's a non-photosynthetic coral. I had some that looked just like that, but perhaps smaller. At night they'd put out red tentacles. The guy who collected it said it was a non-photosynthetic parazoanthus but I'm not 100% confident in that ID.

I also had a non-photosynthetic leather coral that would close like that...it was sold to me as an "anus coral" but I'm confident that's not the name! He just called it that because of how it looked when it was closed.

That is quite the name! Lolol ill defintely check it out at night to see maybe if its a non-photosynthetic coral.
It actually reminds me a lot of a really closed up zoa.

 

[Seafeather]

I got a few better pictures. Google images keeps saying the same 3 things: a stomatella snail, bubble algae, and lately cuttlefish eggs...? Lol

 

[Seafeather]

When i touch it, its very clearly squishy and holds the indent for a little while. Kind of like a sand filled balloon, but softer?