What's on my rock?

[rk4435]

I've had this piece of rock for over one year and it has been in two different tanks. The tank is stable but I noticed this while rearranging my tank tonight.

Any ideas what it is? It was firm to the touch and did nit brush away.
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[gacolt]

looks like a sponge

 

[jrhunter0000]

gacolt;958857 wrote: looks like a sponge

2nd that...

 

[heathlindner25]

I don't even know where to look in the picture..... and everything is way to blue.

 

[jennm]

Yep, sponge. Harmless filter feeder.

Jenn

 

[rk4435]

Thanks guys.