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Re: APD V4 #346 - Roger's Questions on Kitty Litter
> Date: Wed, 14 Jun 2000 20:57:38 -0600 (MDT)
> From: "Roger S. Miller"
> Subject: kitty litter substrate
I'll be cutting and pasting out of order, but not to destroy the logic:
> When Dan Q. originated the kitty litter substrate idea I thought
> his intent was that a small amount of litter should be mixed
> (along with Osmocote pellets) into the bottom layer a sand or
> gravel substrate. I don't have his original article anymore, so
> I can't check what he actually wrote. I don't know where the
> idea came from to build substrates with solid beds of kitty litter.
> Several people have tried it; have any experienced long term
> success with it?
I've been a proponent of Dan's method since I first read the article as
printed in AFM ('though it's been in FAMA and another as well). Those of you
who would like to read the article first-hand - it's now on the Web. Well,
actually it was there once, disappeared and has been reincarnated by his
Steve Pushak announced Dan's death to cancer February of last year, at which
time the article all but vanished. I undertook steps to reproduce it on my
site, but learned that his family had promised to keep both the business and
the articles active. Well, the business isn't quite what it used to be, but
at least the articles are available in their updated form. Dan's original
site has been moved to its own domain now, and the URL is simply
http://aquariumplants.net/ . Links to the three parts are the topmost
entries on the page.
I've been *very* pleased with the outcome of adopting this approach.
> Kitty litter (as with other clay products) doesn't have much
> inherent nutritional value. It's value is in it's ability to capture
> and concentrate nutrients out of the water (that's cation
> exchange capacity, or CEC).
> Some clay products - including some types of kitty litter -
> contain plant-available calcium and magnesium carried
> over from its previous environment. Other clays -- notably
> the sodium bentonites that may be used for clumping kitty
> litter -- may contain no nutrients at all.
What nutritional value does laterite hold? Or is its appeal in the iron
> In order for the cation exchange process to work there must
> be some movement of water through the clay....
[discourse on CECs snipped]
> It makes little difference how the water is circulated through
> the substrate. The plants themselves will induce some water
> There is one thing that makes a big difference. A solid bed
> of clay is almost completely impermeable to water. Water
> won't circulate through a solid bed of clay no matter how
> much pressure (within reasonable limits) you try to put
> behind it. In fact aquatic plant roots may not even grow
> into a solid bed of kitty litter or other clay any more than the
> roots of garden plants will grow through a solid clay pan.
I'm not even going to try to touch on CECs on this one - it's not what I
feel to be the *strong point* of the Kitty Litter Method.
The specific line in Dan's article that caught my eye was:
"Kitty Litter allows the plants to grow healthier roots, but also root
hairs, that they won't grow in sand or gravel."
Why? Simple. I've tried everything from gravel to marine sand, and the one
thing I personally have found to be true is that the finer the substrate,
the more well-developed the root system. Including the "root hairs" that Dan
At the time the article was published, I was in the "marine sand stage" in
order to approach the very fine substrate consistency for which I was
searching. My own experiences seemed to run counter to the "culture's"
doctrine - the compacting that everyone else was having problems with gave
me far superior results, especially when trying to establish new plants or
The quest for well-developed root systems was a throwback to my days working
in hydroponics, an area where maximum yield is sought in the minimum of
space. So we studied the old terrestrial tomes, researching things like
lighting and photosynthetic response curves, the carbon-nitrogen cycle and
its effects on vegetative vs fruit-bearing growth, diurnal cycles and
timing, and even old theories like the "root-canopy ratio" (some may
recognize the term :drip line"). I can tell you from first-hand studies that
the importance of substrates like Rockwool lies not just in its permeability
or transport mechanisms, but the *texture* of the stuff itself.
So here comes Dan, talking of things I'd already known but hadn't "clicked
on" because I was too entranced by what I was reading in the aquarium trade
up until then. And he only points out the obvious - most aquatic plants do
*not* grow in sand or gravel. Yet we beat our heads against the wall in a
constant effort to get the best results from the most barren of substrates,
constantly adding this and that just to get it *prepped*.
Did'ja ever go wading for plants and *not* get stuck in the muck at some
point or other?
Another point to consider - why would aquatic plants have developed the
ability to transport water, air and nutrients down to a well-aerated,
> In order to allow circulation, the substrate needs to be built of a
> small amount of kitty litter mixed with a larger amount of medium
> to coarse sand or fine gravel. Kitty litter probably should not
> exceed 10% of the mix by volume. The sand or gravel allows water
> to move through the substrate and the circulating water can reach
> and replenish the clays. With more than about 10% clay by volume
> the circulation may be substantially blocked by the clay.
Fortunately, this is not the case in practice.
My substrate begins with around 1-1/2 inches of kitty litter, mixed only
with Osmocote and Iron sulfate. (I used to use Tetra Initial Sticks, but
dropped them in favor of the sulfate.) The low end of the tank has another
1-1/2 to 2 inches of straight, fine sand as a sealant/cover. Total depth at
the high end can reach over 8 inches. My only concession to "turnover" is
the introduction of Malaysian Trumpets.
As to how well my plants fair - well, stay tuned for the CD that will be
available with an entry into the AGA's International Aquascaping Showcase
and Contest. That will be the first public introduction to my tanks after
all these years. Once that's settled, I'll finally start illustrating my Web
'Til then, I guess you'll just have to find someone that's been by my house.
If you can get them to say anything, that is - most seem to be at a loss for
words after that...
David A. Youngker
nestor10 at mindspring_com