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  • From: "John D'hondt" <dhondt@eircom.net>
  • To: "permaculture" <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] pc aquaponics
  • Date: Wed, 10 Oct 2012 19:59:45 +0100


Hi Kathryn,
we had the most impossible summer ever here in Ireland. Only two days our temperatures were above 20 C and then not more than one or two degrees above. And sunshine hours could be tallied up on the fingers of ones hands. We saw more sun in the last half of September than during the whole rest of the year, a bit too late for many crops. And I take it that aquaponics would need serious extra energy input here to make it work. Without light especially, no photosynthesis.

I have been using your techniques of compost tea, huge diversity of crops heavily mixed. Wind is very seldom abscent here so air circulation is often more than required :)

I'll have to seriously think about an aquaponic system.

John

John, I had to chuckle when I read your note at the end about Ireland's
dampness and resulting "fungal abundance". We have much the same climate
here as you do. We're not quite as far north, but we've got l-o-n-g, damp
autumn/winter/spring, with typically only a few short weeks of warm dry
summer. We could quite possibly be the mildew capital of the continental USA.
Early blight, late blight, fungal this-n-that are all very common here for
just about everything and anything that grows.

Happily, there are a variety of options in aqupaonic systems. One of my
favorites is to inoculate the system in advance with beneficial bacterial
and fungal colonies, so that any wayward spore or germ has a lot of
competition, right from the start. That can be done either in the root zone or
foliar sprays or both. One very popular choice is compost tea, which I believe
someone else either mentioned or asked about earlier in this conversation.
Well made compost tea is just brimming full of beneficial goodness, and
it can safely be used in aquaponic systems.

Another of the strategies with aquaponic systems is to have a really strong
diversity of plant populations, so that no one plant species is host for
something which will cause problems.

A third option is to have lots of moving air through the growing area.
The stereotypical aquaponics system is generally illustrated as being within
a greenhouse, and most of the systems I've seen or toured had fans that
blew a phenomenal amount of air through that canopy. If there were fungal
spores moving through, they just kept on moving. That also helped keep
humidity down even with the fish tanks in near proximity. Some climates can get
away with aquaponics systems set up outdoors, or with only partial roofing
(such as the UVI system). I don't know what sorts of tropical nasties
they've encountered but they must have their own special population of pests
down there too.

I haven't done a keyword search in Google to see what sorts of disease
problems the various universities have had in their setups; I'm sure some of
them have written up articles about this-or-that issue. That might be an
interesting day of reading for the next rainy day we have here, which will be
sooner than I'd like. But yes, in general, there are multiple options for
aquaponics, just like for other forms of gardening and/or ag, which either
prevent, minimize or mitigate damage from fungal, bacterial or viral
disease. It would be hard to make blanket recommendations about which ones
would be the best or most appropriate, since there are so many other variables
involved.
Kathryn Kerby
frogchorusfarm.com
Snohomish, WA


In a message dated 10/9/2012 4:28:43 P.M. Pacific Daylight Time,
dhondt@eircom.net writes:


I was obviously too fast again when I called a water environment basically

anaerobic. That would only be the case in a static situation. Moving water
can have enough oxigen to enable salmon to perform very powerful leaps.
However, if you had numbers of micro-organisms in water as high as in good
soil your water would be anaerobic and it would look rather unclear and
murky.
Those huge numbers in soil are important because in a good ecosystem like
good soil, bacteria and fungi have very much closer relations with plants
than just turning amonia into nitrate. It is known that micro organisms
exchange complex molecules like amino acids and vitamins (B12 has been
known
for this for decades) with plants for plant made sugar. In some places
like
India people used sugar as sole fertilizer and saw no lack of nitrogen. I
can well believe that for I used Sitka spruce saw dust (with virtually no
nitrogen) on top of rock and could not find nitrogen being a limiting
factor. Of course we seldom have a problem with too little rain here in
Ireland and that helps.
Fungi/mycorrhizae live partly inside plant roots, exchange molecules and
information and are known to protect plants from environmental stresses
like
acid rain and diseases caused by other fungi and bacteria.

I love my soil ecosystems for they enabled me to get rid of potato blight
and crucifer clubroot without any chemical intervention and even without
rotating crops much for 20 years. What do you do when your aquaponic
system
develops a disease problem? You probably have a better chance in Tassie or
the US but here in Ireland blight and other fungal spores are everywhere.
Still, how would you solve disease if it occured?
John


G'day John & others,

If I read John's reply correctly, he seems to imply that aquaponics
systems
are anearobic. Not so. The bacteria that convert the ammonia to nitrites,
and other species that convert the nitrites to nitrates, all require
oxygen
to thrive. Hence the use of air bubblers in most succesful system to get
the
dissolved oxygen (DO) levels to the maximum. And to prevent the fish from
going belly up, of course. DO is VITAL to the operation of aquaponics.
This
is further mitigated by system design, e.g. the commonly used flood and
drain system gradually floods the growing media with poop water, then the
water flushes away quickly which effectively "sucks in" O2 from the air
above the growing bed. Then the bacteria go to work to do the conversions
so
that the plants can thrive. Without O2 (by definition, anearobic
conditions), the bacteria die -> poop remains poop -> fish die of ammonia
poisoning. BIG PONG.

Areas that get clogged up in the grow beds, e.g. tomatoes have vigorous
root
systems that sometimes lead to "dead" spots in the beds, get anaerobic.
When
you stick your hands in there, it pongs. As you would expect. These dead
areas mean that the overall conversion efficiency of the grow bed (i.e.
natural filter) becomes less efficient. A regular testing regime (e.g.
weekly) for ammonia and nitrates will show you how efficiently the
conversion is happening, and will point out when there are problems in the
system. That is one reason for instance why sand is a Really Bad Growing
Medium in aquaponics, because it simply clogs up with poop and plant roots
too easily.

Earth worms are often put into the growing beds, where they work further
on
the sludge and enable the most to be made of the nutrients contained
therein.

Lastly, there are very few places on this planet where the perfect combo
of
soils & climate occur. (I happen to be in one such place, being NW
Tasmania.) So even in organic soil-based ag, one would have to import
micronutrients in the form of rock dusts, kelp meal etc. to get the soil
in
balance. This can also be done in an aquaponics system. Most systems are
run
in the pH range of 6.0-6.2, which means that rock dust amendments will get
dissolved by the slightly acidic water, thereby making the nutrients
avaliable to the entire system (plants & fish). Quite commonly, sea weed
extracts are also added for the same purpose.

Cheers

Pierre Marx



________________________________
From: John D'hondt <dhondt@eircom.net>
To: permaculture <permaculture@lists.ibiblio.org>
Sent: Tuesday, 9 October 2012 8:22 AM
Subject: Re: [permaculture] pc aquaponics


My problem with aquaphonics is not just disolved chemicals aka nutrients.
Soil is an ecosystem consisting for at least ten % out of microorganisms
and
often a lot more. To a large extend these soil organisms are aerobic. It
is
as good as impossible to maintain a large aerobic community in water.
john

On 10/7/2012 9:52 PM, Scott Pittman wrote:
I too have serious misgivings about aquaponics. It is always presented
as
some kind of perpetual motion machine that provides for all its needs
within
the system, which I doubt. I also do not believe that it could possible
have the nutrients necessary for providing wholesome and nutritious
foodstuff. We are talking about the primary nutrient source being fish
dung
in this closed system, where does the selenium, calcium and
phosphorous
come
from? The co-evolution of plants with soil organisms and minerals has
created the human nutrition story and without soil I think the actual
nutrient content will be woefully inadequate.

I would never try to grow food for myself in an aquaponics system unless
its nutrients came from extracts of soil-based systems (don't quite k
now
how that would work given the anaerobic aspects of aquaponics systems. I
did find through a Google search a site with pictures of a soil-based
aquaponics system but they were growing ornamental aquatic plants in
submerged perforated barrels with a soil mix in them. The root crowns of
the plants were slightly above water level.

I would love to see some data on nutrient content of hydroponic vs soil
based vegetables.

There is probably no comparison with the nutrient dense food crops grown
in enriched soil with balanced nutrients and minerals.

I would also point out that both the rice paddy system and chinampa
systems
are soil based systems with a lot of water to maintain growth they are
not
by any means hydroponic or aquaponic. You might also throw in the fast
disappearing mangroves as an example of aquaponics but again you would
be
wrong.

In Eritrea they are developing an array of sustainable farming systems
that use sea water, They impound water in lagoons and grow shrimp in
them. That nutrient-rich water is released down stream to fertilize and
irrigate salt-tolerant land based crops. These crops are used to human
as well as livestock feed and to make rope or cloth. They are also
propagating, planting and harvesting mangroves for firewood, livestock
feed and construction wood. They are not reducing the populations of
mangroves along the coastline where their project is located. There is a
PBS documentary about this well worth watching, maybe viewable online or
for $$$ for the dvd.

LL

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