I have two Vortechs (MP10, MP40) running in my 90 gal. I'd like some feedback from other Reef Central, Vortech owners as to whether or not they use the foam covers that come with the Vortechs. Currently, I don't. They just look like they could become a nitrate problem. If you use them, what is your experience with them? Do you favor them? and if not, why? Thank you.