Sadielynn FYI...I have nirite snails(~100) and they eat all the coralline on my acyrlic. I could not believe it myself. They leave the rocks alone and the coralline grows well there. I have not cleaned my glass in over a month.
I posted this on this site today and since I have it handy I posted it here.
The glass is clear and if there is a blurr it's a snail.
The urchin stays in the rockwork and does not come out in the light. I have a black long spine and a white one. they both are hitchhikers that came in as small pea sizes.