Blue Lab Truncheon for testing PPM??? Is there a good bang/buck ratio on this? I have their pH meter and so far so good for the last 6 months. As grow #2 gets under way and I take the 1000 mistakes I made in the shake down cruise, apply the wisdom from this site, the books I've read and continue to read I can see I need to pay way more scrupulous attention to nutes especially cal and mag. I have a big (not big in the usual sense...enough for 16 five gal smart pots) batch of super soil "working" but I skipped the epsom salt as I am inclined to avoid the word salt. I'll dose cal/mag via GH or Green Planet. Any thoughts on crab shell for cal. as I keep as organic as possible in soil/ProMix/Coir recipe? Thank you to all that post here with expertise I dont find many other places. BIG thanks. Feliz Navidad y peospero nuevo ano!!