I've been using the Red Sea test kits for a couple of years now, they're really easy to use and very accurate in my experience. The Nitrate Pro test kit is particularly easy to use, and has served me very well. We recommend them
http://www.bigreefdepot.com/Red-Sea-Test-Kits-s/167.htm - great test kits for those looking for Hanna Checker accuracy at a lower cost.