Sponge on shell...

[Zen Reeferer]

I've got this 5" crocea with a couple of different types of sponge starting to
cover one side of it's shell. One's dark purple, one's light purple:

and with the mantle retracted:

Any harm in leaving it be? If I try to remove it, don't the little bits of sponge left behind that are stuck to the shell grow more? The other side gets more light and appears to be sponge-free at the moment.
Have had folks elsewhere tell me to:
A. Remove the sponge, place in dark spot in tank.
B. Remove and toss the sponge.
C. Remove sponge, toss clam.
D. Toss it all and go with seahorses.

Curious what the knowledgeable folks here think.

Thank you...James

 

[Boomer]

Those may be boring sponges. Remove clam from than and get a or make a 1 % solution of formalin. Brush off the areas with the foramnlin. An let clam, sit out side tank, say in a empty bowl or dish for 1 hr. Then rinse the shell very well with freshwater and replace the clam. You may want to put the clam in QT tank for awhile, mostly for the reason you want to make sure no formalin gets in the display tank.