Specialty Gardening: Rejuvenating Used Potting MIx?, 0 by tapla

tapla wrote:
Because of its composition, your mix is extremely water-retentive - much more difficult to grow in than need be, and provides you with a very narrow margin for error when it comes to watering and fertilizing. The key element that allows be to make this assessment is the size of the particles that make up your soil. The MG is already extremely water-retentive, and the worm castings simply fill the pores between soil particles, making the pores even smaller and the soil even more water-retentive.

If I were you, I would look hard for pine bark in an appropriate size and use it generously. You'll find it to be much less expensive than your MG soil, and far superior in it's ability to provide a root environment that offers far greater opportunity for plants to grow to their genetic potential.

I suggest something like
5 parts of pine bark fines (like in the picture at 3, 6, or 9)
1 part of perlite (coarse grade if you can find it)
1 part of your old soil
2 teaspoons of dolomitic (garden) lime per gallon of new soil.

Al