I own a Prism and am using it right now on a 10 gal reef.
I have to say at first, it was very noisey. I got nothing but clear skimmate out of it for weeks. The skimmer cup would fill up and start sucking skimmate back through the venturi tube. It sucked ( literally)
I finally read a little about tweaking it to make it work better. It started skimming darker and thicker and the noise died a little, but it was still very very loud and annoying.
I have never had it die and not come back on, but If had it to do all over again, I would have plumbed a sump, and maybe bought an Urchin.
I have owned several other skimmers, and I have to say that this one is by far my least favorite.