David, I use the salifert test kit. I am sure api is also good. I have a hannah checker for alk and calcium that I would be happy to sell you with personalized instructions. For me (not everyone) I find using the test kit easier and quicker that the hannah. However I strongly recommend the hannah for phosphates, and consider it a MUST as I have not found a regular test kit that reads low numbers correctly. Also I suggest you get a salifert nitrate test kit while your ordering.