I'd say water is fine and lots of people have used it for many many many years with no problems. IMHO clearex and those things are money makers and that's about it. Besides, don't you do hydro, Kuri? They might put things in it that can unbind particles to soil so it might be useful in that case, but if you fertilize correctly, slowly increase the level as the plants get big then towards the last couple weeks start tapering down then just use plain water you should be fine.

Yes waters a very good solvent, but universal? If it were universal, what would you use for a container? Also water can't solubilize lipids or other nonpolar molecules.