I'm new to Sansevierias and have been reading up on potting mixes and experimenting with some potting mixtures. I have finally come up with a nice, fast draining mix but would like some feedback. Currently I'm mixing together (amounts are approximate but pretty close):

4 parts coir "peat"

4 parts Miracle Gro Cactus (& etc) potting soil

2 parts coarse perlite

2 parts expanded shale

Adding a little water to the mix, it remains very friable when you squeeze a handful. When you water a plant, the water begins to run out the bottom of the pot really fast! I guess my concern is, will the coir retain too much water? From reading, it sounds like coir has some definite advantages over peat. I think the combination of perlite and expanded shale should help provide more air capacity for the potting mix.

Prior to obtaining the coir, I was mixing together the Cactus mix, some potting soil, perlite and expanded shale. When damp, it was a nice mix but became quite hard when it dried out. Adding coir and deleting the soil-based potting mix made a significant difference.

I'd love to hear some feedback from experienced growers.