I made the same switch a few months ago from API to the hanna checker. Just so you can compare a little, I had a big difference in readings between the 2 test too. I think it would be that way when switching between any 2 brands. It has always been my understanding that we work with in a wide range that is exceptable by our tanks, and as long as we hit some where in that range and keep the # stable it is all good. I know some of us like to aim for a certain # w/ the idea that maintaining that # will give them better growth, I'll tell you though I can never get my KH above 9 (ever) and I get some nice growth. Surprising growth really, not to say it couldn't be better. I think after a few tests w/ the hanna test kit you will find you like it. Unfortunately I don't know much about reactors, so thx for the thread I'm learning a lot from this one.