If you read the post on Optisorb (if not, read it here), you know that I have been shopping around for a replacement for pumice in my soil mix.  I have read in various places on the net that a lot of people are using Napa Floor Dry so I found some at my local Napa store and purchased it.  It was $8 and some change for 24 quarts, which makes it cheaper than the Optisorb.  

Before we get started, let's talk a little about safety.  This material, like Optisorb, is diatomaceous earth;  which is actually the fossilized remains of prehistoric diatoms, cool, huh?  As cool ad it is, it is not good to breath the dust, over time it can lead to a condition know as silicosis.  I recommend that you wear at least a dust mask while sifting it.  Here, in the Heart of Dixie, I recommed the 3M dust mask, it is much better than the cheapos at Walmart.  You can get them at Home Depot, Lowes, and most paint supply stores.  In fact, it is a good idea to wear one whenever you are sifting.  Protect your lungs, they are the only two that you get.

Warning on The Bag

When you open the bag, here is what you see.  Right away, it is obvious that the particle size is a little smaller than Optisorb, but more uniform.

Particle Size, Napa

Particle Size, Optisorb

Here is a closer look, after sifting, of both of the components.  The Optisorb is on the left and the Napa is on the right.  You can see that the Optisorb has some larger particles that what is in the Napa brand.  For an additional comparison I added some pumice to the second picture, it is at the top of the "triangle".

Optisorb and Napa

Optisorb, Napa, and Pumice

After sifting, I had almost a whole 5 gallon bucket of material, about a gallon less than the Optisorb.

Yield, After Sifting

There are some nice fines left, it should make for some nice mame or shito soil.  There seemed to be less fine dust in the Napa compared to Optisorb.


So, which is best?  The Napa is definitely cheaper, you can get almost twice as much for the same money.  The Optisorb seems to have a little large particle size.  Napa had less dust.  Keep in mind that this is just a one bag sampling of each, I don't know how consistant, bag to bag, each is.  But all things being equal, both will work, the Optisorb inches out the Napa a little due to its larger particle size.  

If you live in an area where you can get pumice, forget about both of these, pumice is the best by far.  I do think that these two components will at least be a reliable substitute.