Skip to Content.
Sympa Menu

permaculture - Re: [permaculture] pc aquaponics

permaculture@lists.ibiblio.org

Subject: permaculture

List archive

Chronological Thread  
  • From: "John D'hondt" <dhondt@eircom.net>
  • To: "permaculture" <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] pc aquaponics
  • Date: Tue, 9 Oct 2012 22:19:23 +0100


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 know
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

_______________________________________________
permaculture mailing list
permaculture@lists.ibiblio.org
subscribe/unsubscribe|user config|list info:
http://lists.ibiblio.org/mailman/listinfo/permaculture
message archives: https://lists.ibiblio.org/sympa/arc/permaculture/
Google message archive search:
site: lists.ibiblio.org/pipermail/permaculture [searchstring]
Avant Geared http://www.avantgeared.com/


_______________________________________________
permaculture mailing list
permaculture@lists.ibiblio.org
subscribe/unsubscribe|user config|list info:
http://lists.ibiblio.org/mailman/listinfo/permaculture
message archives: https://lists.ibiblio.org/sympa/arc/permaculture/
Google message archive search:
site: lists.ibiblio.org/pipermail/permaculture [searchstring]
Avant Geared http://www.avantgeared.com/



_______________________________________________
permaculture mailing list
permaculture@lists.ibiblio.org
subscribe/unsubscribe|user config|list info:
http://lists.ibiblio.org/mailman/listinfo/permaculture
message archives: https://lists.ibiblio.org/sympa/arc/permaculture/
Google message archive search:
site: lists.ibiblio.org/pipermail/permaculture [searchstring]
Avant Geared http://www.avantgeared.com





Archive powered by MHonArc 2.6.24.

Top of Page