Weirdest thing I’ve seen...help ID

[nickenayat]

What is this? It is soft and stringing and a whitish color. I am worried and don’t know what to think of it. It’s grown slowly over the past year and doesn’t seem to be harming anything. I’ve scrubbed t off with a toothbrush at times and it goes away but consistently grows back. Does not seem to be spreading in the whole tank either, just stays in these two specific spots.

Photos:

 

[Maritimer]

Looks like a sponge to me.

Unless it starts to overgrow those zoanthids, I'd consider it a beneficial, filter-feeding member of your reef community.

~Bruce

 

[Travis Stewart]

Looks like a sponge to me.

Unless it starts to overgrow those zoanthids, I'd consider it a beneficial, filter-feeding member of your reef community.

~Bruce

I also second sponge!

 

[Vincent100]

Yep I'm with maritimer ... sponge

 

[Big G]

After "toothbrushing", you might try getting a bit more flow in that area and see if that eliminates the sponges from growing in that particular spot in your tank.

 

[easternreefer]

sponge