From my investigations into the issue, the darker colored pumice with higher iron contents may be even better for CP than the light colored pumice I now use, and may even be heavier and even less likely to float. I'm thinking of picking some up when I'm in town today. I have also been thinking of creating some hypertuffa pot caps (to place on top of the media in a pot with a small opening for the plant to be planted through) to help hold the plants in place and to reduce moss antagonism.
