Here is a reference I stumbled across while researching use of "professional aquatic plant soil" made by Profile. I don’t know who originally posted this. -----Arcillite is a calcined montmorillonite clay. According to a U of Florida web page (http://hammock.ifas.ufl.edu/txt/fairs/2455): There are now a number of companies in the United States which quarry clay and heat it in specialized kilns which cause the clay to expand under high temperature into a highly porous fused structure which is physically and chemically stable. The next steps involve crushing large chunks of calcined clay into smaller particles which are subsequently graded into specific particle size ranges. Light weight concrete products and road surfacing additives are two popular applications. (Stuff about use in high-traffic turf areas, potting soil mixtures snipped) Many calcined clays have properties which make them desirable as potting media components. Those clays which are receiving the most attention are more porous and therefore considerably lighter in weight than Turface. Calcined clays are essentially indestructible particles, which provide non-capillary pore space to a mix due to the large spaces created between particles, and hold water internally within their open-pore particle structure. Most calcined clays have good cation exchange capacity which helps in the retention of nutrients but have no nutrient value of their own. The last time I looked into this, I was looking for info about Turface, which is a similar product with a nice terra cotta color and a texture somewhat like kitty litter. It retains its shape when wet, unlike kitty litter, and is softer than crushed brick or crushed terra cotta flower pots. I ran into a web page for Profile which I can't find now. I did run into a reference to use as a soil amendment for turfgrass, so I assume it is similar to Turface in its physical and chemical properties. I seem to remember that it was formed into small cylinders, rather than the random crumbles of Turface. Turface is much beloved of bonsai, cacti and alpine plant enthusiasts. A powder form is available for drying out muddy athletic fields before a game. It's heavier than most soil amendments like perlite and vermiculite, which makes it more expensive due to shipping costs, but it's much lighter than gravel. It sinks easily and stays sunk. At any rate, I've been wanting to use Turface as a substrate for some time,but haven't been able to get a large bag of it. I got a small sample bag, and it is nice looking stuff, only slightly dusty. Note that while these calcined clays have good CEC, they have no nutrient value. I wonder if the pores are suitable for bacterial conversion of nitrate to nitrogen. If anyone wants to try either of these products, it is probably cheaper sold as a soil amendment than as a specialized aquatic plant soil. Btw, the distributor for Turface in Canada is Plant Products, Ltd. in Brampton, Ont. I think this is the same company Sears and Conlin got their lifetime supply of trace elements from. -----
After using the PMDD method with success then failure, I decided to add some sort of substrate other than the plain gravel I have at the moment. The accounts on profile/professional aquatic plant soil were quite encouraging. Of the 2 people using it for more than 6 months one reported great results and the other said that it was "best looking/fastest growing/no algae tanks so far".
I also found this comparison (E. Bartheri in a pot):
1. Mix of Sera's Floradepot, Seachem's Flourite, Profile's arcillite - fantastic
2. Profile's arcillite. - very, very good.
Profile appears to have contain no nutrients. Could anyone suggest possible additions and amounts that would improve this basic substrate?.
For the purpose of providing iron what would be the best approach (I tried following the thread on EDTA and got out chemistried). Would it be sufficient to add peat (if so what kind?, how much?) or would Microplex be needed (again how much - I would guess at less than a half teaspoon for a 50gal).
And for clarification are phosphates sequestered just by iron containing clays or would CEC alone play a role.