[Robert Hudson]

Tom barr gave it a go and pretty much proved its nonsense.

Oh it must be garbage if Tom Barr says it is, after all his opinion is the only one that matters! Hail the Barr nation!

What is Penac supposed to do Art? I seem to remember the last time it was discussed the explanations were rather vague. There is also a big USA corporation that uses it as a water sewage treatment product if I remember correctly.

So, if I took the sterile substrate that we typically use for our aquariums and sprinkled bentonite (or a substance that will increase it's CAC and provide a series of minor nutrients), is this a bad thing? I think not. What I would be doing is helping to transform my sterile substrate into a nutrient storehouse for my plants and providing for the long-term success of the aquarium.

That part makes perfect sense. Increasing CEC and adding another source of minerals. Nobody seems concerned about CEC any more though, (you said CAC, I presume that was a typo) and there are lots of ways to add minnerals. Even the use of soil is somehow not enough for a source of minerals without "mineralizing" the soil. That is the current fad. Is that over kill? People don't seem to think so. Would adding Penac to increase CEC and minerals be overkill?

About those rice farmers, www.cgiar.org/pdf/10_cn_ait.pdf look at the second page, third paragraph. The use of bentonite to increase yields.

Hoppy, step out of the Barr box for a moment!