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[APD] Soil and the Diana Factor

I have the pleasure of living not too far from Diana and having had her give a talk at a local club meeting. She gave us a wonderful explanation of what her method really entails and why things work the way they do. Since then I've had many discussions with her regarding how and why she does things. There have been a lot of "urban legends" floating around about Walstead aquariums and I'd like to get on my soapbox and clarify some of them.

"Based on Walstad's excellent treatise, doesn't it take many years for the
soil to be depleted?"

Based on a few in-depth conversations with her about this she says that most potting mixes last about two to three years depending on conditions in the aquarium.

"Aren't soils from diff places very diff?"

I'd like to stress that soils aren't what she recommends. A nice, cheap, non-enhanced, potting mix is what she's talking about. The most important element of this is peat moss. It's needed to maintain a low pH in the substrate to keep the decomposition at a slow, steady, rate. It's from this that we get the DOC and trace elements for the aquarium. Soil such as most of us are thinking contains too many other elements and not enough peat to make a stable environment.

"As Ellen said, a coffee-can full isn't much. Actually, Walstad explicitly
makes the point that you can use much more soil (on a volume basis) than
you can many substrate additives, so even if it's a less concentrated
source of a particular nutrient you still wind up with more."

Yep 1.5 to 2 inches of soil underneath 1 to 1.5 inches of inert gravel.

"That said, Walstad expects the soil to be a great source of traces, not
macronutrients. I think that Josh Bjork's problem is limited
macronutrients, which in the Walstad method would be provided by large
amounts of fish food."

Definately. The only fertilizer she's told me she uses is regular fish food. Something _very_ important to point out is she uses well water with a GH of 14 or so but it's not mentioned in the book enough to make it memorable. Those elements are an essential part of how things work in an aquarium based on her ideas.

"As to the differences in soils, Walstad specifically recommends using
topsoil from a well-drained area."

Again, not soil, Potting Mix. True soil is has too many other things that can cause serious destablization in a system like this. When I asked her where she gets hers the words "cheap" and "Wal*Mart" are the ones that stick in my mind.

Thanks for reading my ranting,

Phil Edwards
Charlotte, NC

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