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  • From: KAKerby@aol.com
  • To: permaculture@lists.ibiblio.org
  • Subject: Re: [permaculture] pc aquaponics
  • Date: Mon, 8 Oct 2012 13:18:27 -0400 (EDT)

The question of what to use for media is one of the most hotly debated
(usually in friendly ways) topics in hydro- and aquaponics at the moment.
There's a breathtaking array of possibilities, ranging from good old
fashioned
sand, to gravel, to lava rock, even peat moss, coir and other natural
materials. How those materials are gathered, refined and sold will in part
determine whether folks want to use them for that purpose. Clean beach sand
is one thing; gravel gathered from the side of a busy road, probably not.
Of course there's also the man-made materials, with perlite/vermiculite
being a popular combo, expanded clay pellets being popular and easy to work
with but expensive, and goodness knows what's come out in the last few years
that I haven't kept up with. Each one of them has their pro's and con's,
and each one of them ranks differently in terms of cradle-to-grave analysis.

None of them are the clear hands-down winner, usually because folks come
into this activity from lots of different backgrounds, with different needs
and access to different materials. What works for some family in
sub-Saharan Africa won't be the same "good answer" for someone trying to
garden on
the roof of some high-rise in Hong Kong.

One of the really interesting developments in recent years is the addition
of earthworms to the mix. That is also hotly contested where some folks
claim it's not necessary or even beneficial, while others swear their systems
won't run without it. There is a lot to be said for worm castings, and
the worms keep the system very nicely cleaned of any biological buildup
which
otherwise wouldn't have a purpose and becomes a maintenance issue. My
"take" on it is that such buildup is an "output" begging to become an
"input",
and worms are a nice way to do that. But those populations do need to be
balanced within an ever-more-complex system, and that takes more effort.
Furthermore, some folks wonder if the aquaponics should then be called
"vermiponics" and well, I guess that could be argued either way.

What I find fascinating is that at the end of the day, both "soil-based"
and "soilless-based" ag forms are moving towards each other and becoming
nearly indistinguishable over the passage of time. Totally organic (ie,
carbon-based) systems, such as peat-moss or coir-based media systems
eventually
need powdered rock and/or other mineral, inorganic inputs to stay balanced.
Totally inorganic, inert media systems like gravel and sand need living
components in the media, such as worms, to cycle everything. Almost
regardless of what folks start off with, give the system enough time and
"nudges"
towards overall system balance, and you end up with material that is quite
similar to soil. Because that's what soil is - a combination of living and
mineral materials that have co-existed for many generations. At which
point most of the objections to aquaponics sort of fade into the background
as
"maybe was a concern once, but not anymore." The fact that folks can
arrive at edible food and low-input meats this way, when they might be 18
stories up in some metroplex, or in the middle of a desert, is the part I
find
so very appealing. It really is food production for anyone who wants it,
regardless of where they're living. So in my mind and in my little personal
definition of permaculture, aquaponics is as valid an approach as any
other.
Kathryn Kerby
frogchorusfarm.com
Snohomish, WA USA


In a message dated 10/8/2012 9:45:08 A.M. Pacific Daylight Time,
venaurafarm@bellsouth.net writes:

On 10/8/2012 11:28 AM, Toby Hemenway wrote:

> plants. It contains N primarily in the form of ammonia, and the usual
> bacteria are present in the gravel beds (which are best made with
> lava rock or some other high-edge substance) to convert it to nitrite
> and nitrate.

Could biochar be used as a component, along with gravel or lava rock in
the growing medium? It seems like a perfect ingredient, absorbs toxins,
retains nutrients.

Lava rock has a very high carbon footprint and may contain toxins: it is
sometimes manufactured in kilns fired with toxic petrochemical waste or
by products or flammable industrial waste - or so I hear - maybe this
has changed. Mine the rock to be converted to lava rock, fire it, store
and ship it in bulk or bagged. High carbon footprint.

LL
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