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Re: Substrate idea and water quality questions
Bob Dixon wrote:
> I am thinking about trying a new substrate clay in lieu of laterite. It
is
> pyrophyllite clay, as described on the web at:
> http://www.genhydro.com/pyroclay.html
> It is supposed to slow-release a wide spectrum of nutrient minerals, which
> should help my otherwise pitiful water to support life.
It should also contribute to a wonderful bloom of diatoms. If that's the
kind of plants you want to grow...
The web-site you refer us to appears to be a mini-infomercial for this
stuff, and should, IMO, be taken with a grain or two of salt (or a few tokes
of what a lot of hydroponics growers specialize in). It makes a big deal
over the presence of silica in this particular clay. Silica, according to
most _respected_ authorities on the subject is for most plants considered
"beneficial" and not "essential". The amount of silica listed in the water
analysis you provide is probably more than enough for most aquatic plants.
If you were growing corn, bamboo, or perhaps a grain crop for forage feeding
of cattle, then you might want to bump up the silica, but not for the
typical aquatic plant.
Clay in a substrate does help to bind nutrient ions until they can be
absorbed by plant roots. I don't like the idea of the presence of almost 23%
aluminum in this stuff - that could present you with toxic conditions once
submerged. Dupla, in their many writings on laterite, stress the fact that
laterite is a type of soil which has has most things (which could present
problems) leached out of it.
One possible senario which might prove both interesting and valuable would
be to set up two tanks, one using Substrate Gold (you said that you've used
it in the past, maybe you have some left) and a second using this
pyrophyllite clay. Get a group of plants (hopefully, all from one source)
and take a representative sample and submit it to a lab for elemental
analysis (see Steve P.'s web-site for references) and then plant both tanks
with the rest of the plants. After about six months to a year, take similar
plant samples from both tanks and submit them for the same analysis to the
same lab. A comparison of the elements found in each of the samples coupled
with the growth patterns you observe in the individual tanks could prove
interesting to a lot of us.
As far as your water quality report, I suspect there might have been a
mistake made:
> Silica (as SiO2 ) 42.2 mg/l ; Color (whatever that means) 8.0mg/l
Are you sure that they report Color using mg/l? Color is usually reported in
T.C.U. (True Color Units). If your municipality is capable of making a
mistake like this, I'd suspect the rest of the numbers they report as well.
Toronto's water comes in at 1 TCU, and the provincial operational guidelines
for water suppliers calls for this parameter to remain under 5 TCU. But it
is not a healt related issue, merely aestetic.
> Now, mind you, some folks on this list keep fish in their tanks for the
sake
> of providing food for the plants. I, on the other hand am trying to grow
> plants to keep the nitrates and algae under control, and my fish a Amazon
> drainage soft-water critters. This means I don't want to get too much Ca
or
> Mg or CO3 in my tanks, and I would like to keep conductivity down, which
may
> be difficult when providing for the needs of the plants.
If you are trying to create a blackwater biotope (or even a whitewater
biotope) as would be found in the Amazon Basin, why not just bite the bullet
and get yourself a R/O filter. That will strip pretty much everything out of
your source water and allow you to re-create it to match your ideals
exactly. Much simpler than in trying to deal with what you've got. But
remember that plants do need both Ca++ and Mg++. In nature, even though the
water column might be very deficient in these mineral ions, there is so much
water flowing past the plants that they can get enough for their needs. The
same does not necessarily follow in an aquarium, due to the difference in
scale. You might have to bump up the Ca++ and Mg++ in your tank in order to
obtain good plant growth. Many folks on the list report having to use extra
calcium carbonate to get good plant growth, even in moderately hard water.
I don't know how many submerged aquatic plants live in the typical
blackwater biotope in nature. Perhaps one of the folks who took the Amazon
Trip could report (on true aquatics, not on submerged terresterial plants).
James Purchase
Toronto