I save the perlite for the organic mixes. Pumice is a good base for the aggregate medium. Then if you want less water retention add grit and if you want more add the oil sorb (DE iirc).

The standard recipe created by Al (tapla) and used by many here is 1 part Turface, 1 part granite, and 1 part pine bark. The Turface increases water retention, while the granite reduces water retention, so by adjusting the ratio of these two, you can change the water retention of the overall mix. The bark is not necessary, but may add a little bit of a nutrient buffer, and simply makes some people feel better to see something organic in the mix.

You could try using equal parts Turface and granite. (Napa Floor Dry is a fine substitute if you can't find Turface.) 1:1 is where I started, but I ended up using a 3:2 ratio for a bit more water retention.

Pumice is a fine ingredient as well, but its water retention lies somewhere between Turface and granite, so you can't adjust water retention as easily with it.

-Chris

This post was edited by penfold2 on Sat, Sep 6, 14 at 12:26

Thanks! I am going to try Napa floor dry & granite. My plants are inside & I seem to be having an allergy problem with mold/fungus in the organic matter. I use pea gravel as a top coat but the mold must be still getting into the environment. I'm hoping this mix will work because I don't want to move my plants to the garage.

Sounds good. Sifting the Floor Dry with a fine mesh like insect screen to remove fines will give you the best result. Be sure to protect yourself from the dust as well. I wear a respirator when sifting/mixing soil.

-Chris

I hope I didn't mess up but I rinsed the dust off the Floor Dry. Thanks for your help.

If you're still planning to sift it, you may have to wait until it dries. Laying it on a tarp in the sun will do the job quickly. Otherwise, it shouldn't pose a problem.

-Chris

Thanks, I've already dried it.