No question that lab-grade chemicals have fewer impurties than material that has not be refined as much. The question is whether that matters at all for aquatic gardening. And if it matters, how so. I'd be interested to hear of actual situations where it made an attributable diff. It's not clear whether the more agonizingly refined stuff might sometimes be less/more advantageous. Scott H. [/quote] Those posts influenced me to try the lab grade stuff and I couldn't be happier. At the time I purchased my stuff from Clarkson Lab which had better prices. I got 5 pounds of Reagent ACS Potassium Sulfate for $50, still much cheaper than Seachem Potassium. :) (I have hardly made a dent in it with 40% weekly water changes.) Here are the threads in question: http://www.plantedtank.net/forums/showthread.php?t=17562 http://www.plantedtank.net/forums/showthread.php?t=18160 (some speculate that the person, "Maven," posting this thread is the same person as the "Doctor" in the original thread) It was the second thread that made me decide to try the lab grade stuff, since my potassium sulfate from Greg Watson looked EXACTLY like the pictures in the thread. The lab grade stuff I got also matched the pictures exactly. Most everyone called these posts nothing more than trolls, yet here I am using the stuff. :) -------- Scott H. -------------------- m2f -------------------- Read this topic online here: http://forum.aquatic-gardeners.org/viewtopic.php?p=1505#1505 -------------------- m2f -------------------- _______________________________________________ AGA-Member mailing list AGA-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/aga-member