Thanks to all for all the valuable information and advice.
I have two rows of Cymbs (about 100 plants) planted outdoors on the substrate described above with red volcanic rock in 2008
That is over 2 1/2 years I started experimenting with that substrate, so far, I have not had any problems. Those plants were small when planted, have grown and have flowered during this time.
I pulled out a couple of plants the other day and had amazingly long healthy roots. Some almost 2 feet long.
I use
ONLY rain water on the plants. I have plenty of rain water storage for the dry months.
I have re-potted flask seedlings and other Cymbs during this time and have never noticed any root problems. They come out fat and healthy white with pieces of lava rock and charcoal attached.
Except for a few older thinner roots which have naturally "done their thing", and I cut them out.
The plant above has not known anything else but red rock/charcoal as its substrate, and it's booming at less than 2 years from flask!
When I "recycle" the substrate I:
1- Submerge the substrate in half a drum filled with a heavy Cycosin (fungicide) solution for about a week or more.
2- moving the media around every day and taking out all organic material that might come out.
3- Wash the media with pure water and sift with the appropriate grid to get everything out besides the media.
4- Let it completely dry before using.
5- I always use 50% new media when re-potting.
I do not discard the possibility of having problems with this media in the future, especially knowing that this advice comes from reputable sources of this board, but right now, there is no reason to run and repot all my cymbs as they are doing just great.
I will do a little bit of further research as I will try to get the chemical content of this lava rock from the quarry I buy it from. Maybe they have this information.
Additionally, I will get the complete list of plants (including orchids) that people around here grow using that media. This rock is very popular in hydroponics and other commercial operations around here. It is not my invention
More on this later, and thanks again!
Rodrigo
PS. A little bit more trivia. This rock comes from the foothills of the Barva volcano.
This rock is hard and very porous. It does not pulverize. You have to crush it to pieces and it produces a coarse sand-like material.
I am not even certain that OZ even still uses it. The only use I ever put it to is on the aisles between my benches to eliminate the mud!
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