I GO thru stages that I test more than other times.. my recommendation is to try API TEST KIT ... and test regularly for a while... especially if your tanks are fairly new.. and test less as you get more comfortable with keeping your tanks healthy
I have both the API Freshwater Master Test Kit and the Hagen Mini Master Test Kit. I don't like the Hagen kit for many reasons which some are listed on a kensfish.com review of the product. I have compared the two and both seem to match up in terms of readings, but the API is much easier to use IMO.