Tomatoville® Gardening Forums - View Single Post - Diatomaceous Earth as a seed starting medium

RayR · October 4, 2012

You'll be far better off in making a fair and successful study.

There are other problems with pool grade DE:

It is flux calcined. The DE is mixed with Sodium carbonate (Soda Ash) which is a strong base and is heated at high temperatures. This alters the pore structure as well as changes the amorphous silica to crystalline silica.It's OK for water filtration, but not much good for anything else.

PH Is another factor that is important. I don't know what the PH of pool grade DE is but seed starting mediums are PH balanced between 6.5-7.0. So if you're going to use an inorganic medium to compare it too you want it in that same PH range that is optimal for seedling germination and growth.

Another important factor is whether the DE is from a fresh water deposit or a saltwater deposit. You only want DE that you know comes from a fresh water deposit for horticultural use. Salt water DE obviously has a high concentration of Sodium and that ain't good for plants. Where that pool grade stuff comes from—who knows?

October 4, 2012	#155
RayR Tomatovillian™ Join Date: Jun 2010 Location: Cheektowaga, NY Posts: 2,466	You'll be far better off in making a fair and successful study. There are other problems with pool grade DE: It is flux calcined. The DE is mixed with Sodium carbonate (Soda Ash) which is a strong base and is heated at high temperatures. This alters the pore structure as well as changes the amorphous silica to crystalline silica.It's OK for water filtration, but not much good for anything else. PH Is another factor that is important. I don't know what the PH of pool grade DE is but seed starting mediums are PH balanced between 6.5-7.0. So if you're going to use an inorganic medium to compare it too you want it in that same PH range that is optimal for seedling germination and growth. Another important factor is whether the DE is from a fresh water deposit or a saltwater deposit. You only want DE that you know comes from a fresh water deposit for horticultural use. Salt water DE obviously has a high concentration of Sodium and that ain't good for plants. Where that pool grade stuff comes from—who knows? Last edited by RayR; October 4, 2012 at 11:25 PM.