Growth on Acan normal?

I have what appears to be skeletal growth and a new polyp forming on my Acan. However, it's taking off in a new direction and will cause the Acan to lose its spherical shape.

I'm pretty sure this is just new skeleton forming. I couldn't get a picture of the other side of the growth because the acrylic distorted the image. However, you can see that the entire opposite side of the growth is a polyp. This has been growing for some time, and normally you can barely see it as the polyps are fully extended and covering it. A hermit crab or something in the tank spooked it right before this, so I grabbed the camera and got a quick shot.

Is this normal growth or something I should be worried about?

Thanks.

 

Possibly a sponge?

 

Didn't think about that. I suppose it could be a sponge pushing on the polyp. It looks like the polyp is growing out of it from the other side, but it's hard to tell.

I'll move the coral closer to the aquarium wall and get some better pictures tomorrow.

 

Turns out it was a new chunk of skeleton (I think) as there are multiple small polyps growing around it now.

This acan is currently placed on the sand bed, and its skeleton is getting close to the edge of the rock its mounted on (in the pic). What will happen when it hits the edge of the rock? Will it encrust down and continue to grow on the sand bed, or will the growth stop at the edge of the rock?

 

From the scans & blastos I've had, they will start growing down the sides of rock. But they don't amount to very much cause the lack of light on sides. I would see about attaching another rock to it so it can keep growing.