Another one to look at is the Bubble-Magus line of skimmers. I have their little nano skimmer the BMQQ and not only is it built really well, it does a great job in my little 16G nano for uber cheap. Check out
www.nuocean.com as they are the US supplier that can sell them here in Canada at the right voltage.
There is a good thread on RC from owners who are for the most part happy.