Question about Water ID Pool Lab 2.0

Well, there are somehow 40 different ones or so. First of all, replacement chemicals (tablets and/or liquids) for the ones that are supplied. Because they all have an expiry date. And secondly, specifically in my case, PPHPPLR150, TbsPPPLR250, PPHPPHR150 and/or TbsPPPHR250 for determining the phosphorus content. As LR is for low concentrations (0-4ppm) and HR for high concentrations (0-80ppm), and I don't know what I have to start with, probably both.
And THE basic question: Which is better, tablets (problem of dissolution) or liquid (stability in the opened bottle)?

Which one were you looking for?