Yellow sponge like thing, even squirted stuff at me

[Skifflexie]

I've had this thing on this rock I got for a while, it never does anything or grows or moves. When setting up my new tank I transferred the rock (wearing gloves and using a toothbrush) I tried to see if he'd just fall off if I scraped at him. He started squirting stuff so I just ended up putting the whole rock in the new tank with him on it.

What is it?
Is it harmful?
Thanks!


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[Reefing Madness]

Just a sponge, no harm.
Syconoid sponge

 

[Brennan32]

I found one of those too its very small but I didn't know what it was so i guess i do now.


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[Skifflexie]

Thanks!


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[54seaweed]

I have a big red one , yellow one , and a grayish one they are harmless , just having them in your tank tells you that your water quality is good .

 

[melosu58]

And if your water is not the very best they are great filter feeders.

 

[Skifflexie]

Thanks


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