I have never used sand in any of my mixes. And I wholeheartedly agree with your gobbled-gook assessment... although I personally might use the word 'hooey'. I built myself a potting bench at a comfortable height several years ago. It is six feet long and I positioned the shelf so that it would fit a big kitty litter container. I keep all my different 'ingredients' in the litter containers, and have three big bowls on the bench- using them to mix custom batches of potting stuff whenever I have the need. I have been getting more crazy with the mixes as time goes on. But I haven't yet tried aquarium gravel. I am SO gonna go there!

I grow many of my potted plants in rock. Have found that aquarium gravel and pea gravel are too small. Compacts and makes for a very moist environment. The smallest size I use is 3/4" but it all depends on your watering. I have noticed that Santa Barbara Orchid Estates also uses crushed granite from 1/2" TO 3"4".

If Aquarius gravel works for you, great. Would not work for me, I'm a heavy waterer.

Nick

Many Cymbidium mix recipes specify a proportion of coarse river sand which would be mostly Silica as is Diatomite. I remember asking the ex-resident boffin why Diatomite seemed to be beneficial....and he sniffed SAND.

My most recent disaster was with the new wonder potting mix...coconut chunks.
Great for some Genera not so good for others....

Once, I used SOME coarse sand as part of a mix for Phaius for the "fun of it".

Of course, Phaius will grow in virtually anything except....mud?

--Stitz--

Stitz, Just for you "....This species grows in moist to wet habitats, particularly permanent swamps where it may occur in extensive patches in black peaty soil..." maybe mud will be OK.

thanks, Arthur. "peaty soil" is ok.

I expect that The Warden will be unreceptive to a suggestion of a bucket of mud indoors for the next six months.

How about polystrene with chunks of basalt? That is what Beallara Diana Dunn arrived in....and i didn't repot because it was late autumn and the plant had to get through winter in an unheated drafty glasshouse. Needless to say the plant will bloom in a month or so.
The search for the magic mix goes on but i'm going back to treated pine bark as a base. Coconut stuff holds too much water for my watering habits.
The Warden here has shown amazing patience in the 38 years she has had to put up with me and the orchids.

Well yes Arthur I was wondering about the sand partially because at some point in time I know I will run out of diatomite. I really love that stuff. It makes my leaves all big and strong.I need to figure out how much silca there is in granite compared to limestone,compared to whatever other stones I might want to use.

What other potting stuff interests you? Wonder whats so great about basalt?gb

Plants do absorb silica, and there is evidence that it helps protect them against drought, pests, etc, but I doubt that the amount provided by a potting medium will yield any noticeable effects. If you really want to test the effects of Si, try a Si supplement like Dyna Gro's Pro-Tekt. I used it for a while, but stopped when I ran out, because I couldn't see any difference. It's possible that it was providing some benefits, but my plants seem to do fine without it.

As for sand, I would think that would be way too fine for orchids, or just about any potted plant for that matter. Perlite is mostly SiO2, and would be a much better choice than sand.

Thank you penfold2. I was actually working with Pro-tekt for awhile but it was ineffective for me because I know I'm very inconsistent with my chemical use. I had to go to the slow release granular stuff because I'm just that sucky about fertilizer usage. Sooo...when I started mixing in medium size diatomite rocks with my potting media I did see a difference.

The perlite suggestion sounds wonderful I'm assuming spongerock would be the same effect? or am I thinking of the wrong thing?gb