I have it in my AQ filters on my smaller tanks. The lighting from the tank is enough to sustain it. You shouldn't be using a sponge in the AC, unless you plan on rinsing them every 2-3 days.
alright well what should I stuff the aqua clear with then? The sponges I just wipe clean every week when I do my water change. I just let them run under water until they are white, well almost white, again. I know this kills off the bacteria but the sponges are only for mechanical for me.