I saw that, thank you. I'm only heating a 10g. I know many people have used 200w Hydors on Nanos.Here is one but it is a 300 watt unit.
http://www.plantedtank.net/forums/s.../145777-fs-aqua-medic-am1000-co2-reactor.html
I have a 200watt sitting around. Let me check to see if it's 12mm.I saw that, thank you. I'm only heating a 10g. I know many people have used 200w Hydors on Nanos.