Re: Suggested test kit brands?
I've had excellent results with the Aquarium Pharmaceuticals NO3 and PO4 test kits. I know there are 'some people' that poo-poo those kits because they are so cheap and easy. To get confident with their results, you can use The Fertilator over at APC, or Chuck Gadd's calculator to test and calibrate the kit itself. I've never had to make any calibration adjustments, even with older kits. The NO3 kit is usually at Petsmart or your LFS, the PO4 kit usually has to be ordered online from stores like That Fish Place. $7 each.
TW
EDIT: Both kits use printed color charts that become impossible to read at the higher values. In the range we are interested in however, they are accurate and easy to read. Almost like the manufacturer knew what they were doing...