[Jane in Upton]

Interesting!

Yes, Brian, on the allelochemical buildup, I agree with you - who knows if its allelochemicals, or soil exhaustion? I just wanted to clarify that the faster allelochemical bulidup was related to the plant growth, not directly linked to the CO2 itself, for racialfish.

The whole hassle idea is why I still don't do CO2- if I did, I'd spring for the pressurized system, and don't have the budget for it at the moment.

I just re-did my 30 gal, and added a small amount of laterite into the soil as an insurance against iron deficiency. I forgot to add the usual 1 Tbsp/sq ft of ooidic (CaCO3) sand I use (DOH!) but oh well.

So Aaron, what was the source of your natural clay? I used to run two kitty litter substrate tanks, a la Quackenbush. I'd just set them up when I discovered the El Natural forum, and read the Walstad book, thereby becoming a soil underlayer convert, LOL! The 30 gal was one that did remarkably well for 2+ years, and I've also just broken down the 20H, which wasn't as versitile, but did OK with Crypts, Echinodorus, Aponogeteons and hairgrass. I picked up some raw pottery clay, the very red stuff, with the thought that I might use it like the old Duplarit K balls as a supplement, if necessary. So what natural clay did you use? And at what proportion in the soil?

Oh, and Brian, are all your tanks, both pressurized CO2 and non-CO2 tanks with soil underlayers? Your reasoning on the volume of water, and therefore CO2 equilibrium makes complete sense.

-Jane