I had an orange sponge that died. They are impossible to keep with metal halide lighting. If I placed in a low light area of the tank (which it needs), it wasn't getting the high flow it needed. If I placed it in a high flow area, it would get cyano all over it from the lighting.
It took about 2 months before it started turning translucent and dying.
I don't recommend sponges from my experience.
ps- if you buy one anyways, NEVER expose it to air at all. Taking spoges out of the water is a guaranteed death.