BP - I read through your thread and thought I'd mention a couple of things. First, all oil-dry products aren't created equal. Some are less appropriate because of the particle size gradation, and some are inappropriate because of their instability (turn to clay after prolonged exposure to moisture). Freeze a tablespoon of the screened product in a plastic cup overnight. If it's stable when it thaws, it's ok to use. Screening the fines out of your ingredients is a practice that retains the important macropores, the spaces between the particles. The more interparticular spaces filled with air and the fewer with water, the more approval your plants will show for the effort of screening. I/ve done some side bt side tests of various plants grown in a 5:1:1 mix of CHCs:perlite:peat vs the same ratiuo of pine bark:perlite:peat, and there was a significant difference in growth rate, vitality, and appearance with the CHC mix coming in a distant second. You won't need the extra water retention afforded by the CHCs, so I'd stick with the bark. CHCs are very high in K, and potentially very high in soluble salts (if processes with sea water). All CHC products are very low in Ca, potentially high in Mn (which can interfere with iron uptake). Several studies have also shown that the significant presence of phenolic allelochemicals (inhibits growth of other plants) in fresh coir can be very problematic for a high % of plants, causing poor growth and reduced yields if yields are a consideration. CHCs high pH (neutral is too high) also eliminates dolomite as a potential liming agent. Al

Soils are touchy subjects and difficult to agree on, but maybe I can help you reason through by explaining a little about how water retention works. First, the size of the particles and the particles' porosity determine how much water a soil retains. Soils hold water in the air between soil particles (in vapor form), inside of soil particles, on the surface of soil particles, at the interface where particles contact on another, and if the spaces between particles are small enough, soils will hold water in those spaces instead of air. The least desirable water in soils is the water held in spaces between particles. This is because it deprives roots of the oxygen they need to function normally, which limits growth and vitality, and can even cause the death of roots and fungal root rot diseases. Fortunately, it doesn't much matter what soils are made of. As long as they hold favorable volumes of air and water, you can grow in them. In fact, if you want to water every hour, you can grow perfectly healthy plants in a bucket of crushed glass. To make your job easier, you might consider some tips. Soils that hold almost NO water between soil particles (except where the particles touch) and hold almost all water inside of particles are going to be easier to grow in and offer greater opportunity for plants to realize their genetic potential. In order to achieve that end, the particles a soil is made up of need to be fairly uniform in size and larger than about 1/10" in diameter. At a diameter of less than 1/10", soils start holding water between particles, and the smaller the spaces between particles, the more water is held there. You can take a mixture of particles that hold no water between the particles and destroy the drainage and aeration by adding fine material (smaller particles). Imagine a pint jar of BBs. There might be a half pint of air between the BBs. If you add a half pint of sand to the mix, or coco coir, all of a sudden the larger air spaces are all gone, and the smaller spaces, because they hold water more tightly, are filled with water. I think you COULD make a very good soil with nothing but pumice and crushed terra cotta, but how well it will perform is going to depend a LOT on the size of the particles. IOW, you'll need to screen them so the particles you use are between .I-.2" in size, and it will be more important to eliminate the fine material as opposed to that material that might be a little more than .2". I don't see the coir as being a plus in the mix I described. Fertilizing can be monkey easy if you get an appropriate fertilizer. Al

Robin, Sounds like we agree on the basic principle behind using more or less uniformly-sized potting media so perhaps I can just share some benchmark in case you'll find them useful: I use 3/16ths for big plants in big pots (i.e. gasterias, adult adeniums). I also use it for by bigger haworthias though, that are in smaller pots, because they have fat roots that will disintegrate if wet for too long. But I have more use for 1/8ths too, because most of my plants are tiny, planted in tiny pots--adromischus, crassulas, avonias, mesembs, othonas, tylecodons all have wispy feeders that will desiccate if the air spaces in my substrate are too large. I grew my sans in a similar substrate you described and it did well even with the fine particles. I believe it is because they aren't really averse to being watered profusely. They will tolerate arid conditions but if they are watered heavily during growing season, they do take off.

I wouldn't use top for anything, except for top soil. What they sell around here is terrible. I still think your soil mix is finer than mine, even your regular soil, aside from the rooting soil, which would be nice too for that purpose. I use some Perlite fines for seed starting because there's no way I'd use Pumice and Perlite that's 3/16 - 1/4". Now that I started using at least half Pumice and Perlite, it might be nice to eliminate the peat moss stuff altogether, but I don't know what a good third ingredient would be. I have to see what they have locally at a garden store, which is difficult with a bad back. I got the Pumice and Perlite from Amazon, not being able to really see it first.