Hitchhiker ID

DRoth335 · Feb 25, 2022

Can anyone help with an ID of these two hitchhikers? They are about 1.5" long and 1" wide and soft to the touch. They've been in the tank for at least 2 years (I believe they may have come from TBS rock I had in another tank but not 100% on that). If they've gotten bigger over time it hasn't been by a lot. Any input would be appreciated. TIA!

minus9 · Feb 25, 2022

Looks like sponge to me.

EricR · Feb 25, 2022

Neat -- do they ever move across the rock,,, like slowly over time?

WheatToast · Feb 25, 2022

EricR said:
Neat -- do they ever move across the rock,,, like slowly over time?

Sponges are sessile invertebrates; they only grow outwards.

DRoth335 · Feb 25, 2022

They're not any sponge I'm familiar with but that might be what they are. No, they have not moved. Thanks for the input.

minus9 · Feb 25, 2022

DRoth335 said:
They're not any sponge I'm familiar with but that might be what they are. No, they have not moved. Thanks for the input.

There are literally thousands upon thousands of sponges that can inhabit our tanks, but few come out in the open, so enjoy! You should’ve seen the sponges during the peak of ocean rock, lots to enjoy.