Your best choice for periodic testing is probably the Taylor K2006 -- links to Amazon below, but only order if the Amazon seller is "Amato Ind"; other sellers seem to mixup the K2005 (no FAS-DPD) & K2006. Regardless, you need kit that includes an FAS-DPD test, and a CYA test; 'goofy strips' are just not accurate enough.

Ben