What is this ?

[N1Husker]

I discovered this at the back of the aquarium hanging on my live rock. It appears to be engulfing the rock and looks to be about an 1.5" long. Does anyone have any idea what this is and is it good or bad?

 

[kevnkev]

Looks like a sponge. Are those nubbins along the lower edge small round chimney openings (these would be the excurrent siphons of a sponge's filter-feeding body)? What texture is it (sponges should have some give to them, but feel more rough than slippery)? If it's a sponge it's great for your tank - bonus filtration and bacterial habitat! Sponges tend not to have symbiotic algae (especially not white sponges), so it doesn't need to be in bright light unless you want to see it more clearly.

 

[Airphotog]

I second sponge. That is a good sign.

 

[N1Husker]

The protusion on the right, toward the bottom looks like a cylindrical vent and the nubbins on the right side appear to be smaller ones. I have small pinapple sponges all over the tank, but this one is much, much larger. I can't get my hand back there to check the texture, but looks like a mass of translucent milky white glob. I thought it might be a sponge , it just seemed very large.

 

[kevnkev]

Definitely not a pineapple sponge, but it sounds like some sponge species or other. Most species are more like this kind than the pineapple, in that they grow as blobs instead of regular shapes.

 

[N1Husker]

Yeah, I knew it wasn't a pinapple sponge, I've got those and this guy is about 100 times bigger. I will let him just hang out there as long as he likes, as long as he is not harmful, he is welcome (might be a she, or an it, whatever).

 

[NC2WA]

agree with the sponge...

Earl, you should be OK with this...good to have in the tank

 

[N1Husker]

Thanks Kirk. That's what I was thinking but I wasn't use to seeing one that size.

 

[NC2WA]

oh yeah, i had one on my rock that was as big as my hand...

 

[leena2674]

I have a couple of what appear to be the same variety in my tank. If you happen to decide you don't want it there, Tiger Cowries apparently enjoy munching on them.... at least mine did.

 

[N1Husker]

leena, it is just hanging around on the back of my live rock, it isn't bothering anything so I will just leave it alone. Thanks Earl