Sponge issue?

Was wondering what this sponge thing is and if it's bad the leave in the tank? It's in the back side of a rock with no light. The rock used to be covered in GSP but has since dwindled because of lack of light.

 

I something very similar. My vines out. It grows on the bottom of my cap, doesn't seem to do any harm. I do remove some here and there for precautions.

 

Sponges are beneficial filter feeders so I tend to leave them. If they are growing into corals you can always prune them with a tweezers.

 

I could be wrong, but that looks like the type of sponge that can send out runners and start new growth pretty quickly. The only reason you'd need to be concerned (in my opinion) is if they start growing near your corals, specifically any SPS. They would probably choke the light/life out of them.

I have some in my tank too (and many other types of sponges) but they tend to keep out of the way and live on the underside of the tank. As Dave posted, they're great filters in your tank and generally a sign of a healthy system.

 

If they start to take over just use a tweezer or tooth brush to remove them.
I just leave them be. I have a bunch in my tank and they usually grow under rocks.

 

Is there an animal that takes them out? Looking for the easy way lol.

 

Most any large angel will do the trick....