White round thing ID

[mattybecks]

These guys have been in my tank for quite a while, kept meaning to get an ID and today finally getting around to it.
Any idea what they can be? they are smooth, but not squishy.
You can see them in the first part of the video on the rocks. Tank is about 7 weeks old in total now.

 

[aqua_code]

Does it look like this? Pineapple Sponge?

What are these small white cotton balls in live rock

I was going to ask about the green hairs also but I think that is caterpillar weed, but what are these white small cotton type balls?

www.reef2reef.com

 

[mattybecks]

Does it look like this? Pineapple Sponge?

What are these small white cotton balls in live rock

I was going to ask about the green hairs also but I think that is caterpillar weed, but what are these white small cotton type balls?

www.reef2reef.com

no I'm afraid it doesn't. I did some research thinking at first it might have been, but I know they aren't. they are quite round, and smooth - not squishy, but firm and slimy.

 

[Bryson.bobby]

Bump

 

[ScottR]

Do all of them have a hole on the back? I see what looks like one on the bottom one. Could be a limpet. Almost like a snail but limpets usually stay on the rocks and don’t move. They come in many different shapes, sizes and colors.

 

[homer1475]

I was thinking they looked like sponge, but I don't see the typical vent hole that a sponge has.

 

[ScottR]

I was thinking they looked like sponge, but I don't see the typical vent hole that a sponge has.

I can see that. Here are a couple of sponges in my tank. The first one is bigger than a golf ball. The second one doesn’t resemble what is in OP tank. Which leads me to ask, is it soft or hard?

 

[homer1475]

Yeah but see in your photos, they both have that typical vent hole a sponge has. I have some of both in my tank. Some are flat and kind of hard(still soft, but not real soft), while i have some that have the typical conical shape with a vent hole.

While a close up shot from the OP would help with the ID, I still don't think they are sponge.