Not to turn this into a debate about CPR overflows--i've already noted that I think drilling or reef ready is preferable if you're starting from scratch. If anyone else reading this is thinking about a hang-on overflow, though, I'll add this. Yes, the aqualifters can clog and, like any pump at any time, can fail. However, you'll usually notice bubbles starting to build up where it pulls in water. The overflow will keep running for a while. I solve the problem just by keeping a couple of spare pumps on hand. As I wrote on another thread, I think hang-on overflows take a bad rap from reefers. They do have some advantages. They take up much less space in the tank; they are easily removed and can be more thoroughly cleaned with a soak in vinegar or hydor magic-klean. And with the new design, you're less likely to suck a critter into the overflow. The next tank I get will be reef ready. For now, I'm sticking with the CPR. To each his own.