I've been thinking about this. I wonder what the kit shows/does when it exceeds 2.5 ppm. Is simply knowing that you are out of the 1 to 2 ppm range because you exceed 2.5 ppm good enough?I would not get a phosphate test kit of any kind that did not have a clearly discernible range between 0ppm and 10ppm.
my tap water is already 2ppm, so a test between 0ppm and 2.5ppm is simply too narrow for any practical fish tank use.
that may depend on your tap water and tank water quality tendencies. you see I have always suffered from a high phosphate problem, and I rarely get it down to 2ppm. I actually find 0-10 range useful while using my liquid test tube kit. if my phosphates are 2-5ppm I'm happy, if they are 5-10ppm then my tank may need attention soon, and beyond 10ppm reading may require immediate intervention. If they get above 10ppm, I may need to use a phosphate sponge media, as normal tank maintenance just ain't gonna cut it. keep in mind such phosphate spikes don't happen now that I'm more experienced, but back when my tank was cycling, algae infested, and basically running amok, having a wider range test was a godsend. don't be so afraid of liquid test tube test, since once your tank water stabilizes, you'll learn to "feel" how your water quality is from observing your fish, plants, and water. by then most of your test kits will go unused, at least until your tank has an unexplained crisis, or you establish yet another new tank.Is simply knowing that you are out of the 1 to 2 ppm range because you exceed 2.5 ppm good enough?