ID please pics!

[murph145]

heres a few more pics of the sponge / tunicate still duno what it is....
its got a lot of chambers that lead to one exit tube.... maybe u can see a lil better now i have a side profile too u can see the big exit tube it has....
i cant get a better pic of the slug things my camera wont get a clear close up and the run away when i turn the lights on....

 

[fmelindy]

looks more like a sponge to me.

 

[yosemite sam]

Yeah, it's some sort of latticework sponge as well. I have had a few similar to it in some of my tanks, although they usually grow not in direct light. Just watch it, if it starts to smother your GPSs you can trim it or remove it, but it shouldn't be a problem.
As for the slugs, did you compare them to stomatella snails? If they are in fact nudibranchs, I'd remove them. It's better safe than sorry, and some of those little guys can really mow down polyps.