[pondgardener]

Robert,

Check the link below for some additional information. Post #18 has a link to a presentation pdf that Tania had done and may have some pertinent information as well.

http://www.tomatoville.com/showthread.php?t=31658

I have tried the mix listed below that I clipped from another container growing forum with good results.

I'm a little late in chiming in, but I wanted to experiment before I posted. Now that I've had great results, I'll share my experience. Ray's Earthtainer guide calls for a 3:2:1 mixture of ProMix, bark, and perlite. However, people are constantly asking for home-brew mixes. And to be honest, based on Ray's formula, it couldn't be easier. ProMix is fine, if you want a bagged mix. The only thing it really contributes is a wetting agent, and some mycos. The wetting agent, IMO, is completely unnecessary for a SIP. The mycos can be supplied from ANY good organic fertilizer.

So, based on several sources, the ProMix is roughly 70% peat, and 30% perlite. It is 3 whole parts of the 3:2:1 mixture. So, if I figure what part of the complete mix it is, I find that the 3 parts ProMix translates into 2.1 parts of peat, and .9 parts perlite. That makes the overall mixture 2.1 parts peat, 2 parts bark and 1.9 parts perlite. Or, 2:2:2, which reduced to lowest terms, is a 1:1:1 mixture of peat, bark, and perlite.
How simple is that? And it works extremely well.