Aquaponics Digest - Sat 05/29/99
Message 1: RE: Organic Aquaculture
from "Sam Levy"
Message 2: Re: trout effluent
from "Sam Levy"
Message 3: Re: Organic Aquaculture
from "Capista"
Message 4: Re: trout effluent
from Adriana Gutierrez & Dennis LaGatta
Message 5: Re: Organic Aquaculture
from "TGTX"
Message 6: Re: Organic Aquaculture
from Gordon Watkins
Message 7: Re: Organic Aquaculture
from Gordon Watkins
Message 8: Re: Organic Aquaculture
from "Wendy Nagurny"
Message 9: RE: Organic Aquaculture
from "Ronald W. Brooks"
Message 10: Re: Organic Aquaculture
from "Jim Sealy Jr."
Message 11: Re: Organic Aquaculture
from "TGTX"
Message 12: Re: Organic Aquaculture
from "Uwe Bruenjes"
Message 13: Re: Organic Aquaculture
from William Evans
Message 14: Re: Organic Aquaculture
from "Uwe Bruenjes"
Message 15: Re: Organic Aquaculture
from "Uwe Bruenjes"
Message 16: Re: Organic Aquaculture
from William Evans
Message 17: Re: Questions - Reposting
from "Clark Allison"
Message 18: Re: Organic Aquaculture
from "TGTX"
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| Message 1 |
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Subject: RE: Organic Aquaculture
From: "Sam Levy"
Date: Sat, 29 May 1999 01:54:43 PDT
Ron-
i assume that this is a tilapia feed--have you treid ti w/other fish?
sam
>From: "Ronald W. Brooks"
>Reply-To: aquaponics@townsqr.com
>To:
>Subject: RE: Organic Aquaculture
>Date: Fri, 28 May 1999 18:24:46 -0400
>
>Dave
>
>Here is the ingredient list from feed that I use for fry.
>
>fish meal , wheat germ meal , wheat flour , corn gluten , feeding oat meal
>,
>dried potato products , dehulled soybean meal , shrimp meal , torula dried
>yeast , cracklings , monobasic calcium phosphate , algae meal , L-lysine
>monohydrochloride , lecithin , gammarus, L-ascorbyl-2-polyphosphate(vitamin
>C) , ethyoxyquin and citric acid as preservatives.
>
>Min. crude protein - 47.5 %
>Min. crude fat - 06.5 %
>Min. crude fiber - 02.0 %
>Max. Moisture - 06.0 %
>Min. Phosphorus - 01.5 %
>Min. Vitamin C - 100mg/kg
>
>This is a slow sinking food
>
>Ron
>The One Who Walks Two Paths
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| Message 2 |
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Subject: Re: trout effluent
From: "Sam Levy"
Date: Sat, 29 May 1999 01:58:46 PDT
andrew--
you might want to consider a floating medium--i believe it will be easier on
the back whenever cleaning/turning is required
sam
>From: "Andrew.D"
>Reply-To: aquaponics@townsqr.com
>To:
>Subject: Re: trout effluent
>Date: Sat, 29 May 1999 11:45:43 +0930
>
>I did receive them thanks Adriana. What I was hoping for was some ideas on
>how the best way to set up with all this waste water as.
>
>I was thinking that the water from the duckpond (300,000L) would be run
>through 100 metres of gravel bed laid into a plastic lined channel.
>Is this the best way? I would love to hear some other ideas.
>
>Andrew
>----- Original Message -----
>From: Adriana Gutierrez & Dennis LaGatta
>To:
>Sent: Friday, May 28, 1999 9:21 PM
>Subject: trout effluent
>
>
> > Andrew,
> >
> > There were two responses posted to your question on the trout effluent.
> > Did you miss them?
> >
> > Adriana
>
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| Message 3 |
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Subject: Re: Organic Aquaculture
From: "Capista"
Date: Sat, 29 May 1999 06:09:21 -0400
Dear Deborah,
I am involved with 3 other people here in Upstate New York in what will be
an organic tilapia farm.. We are using the Ecogenics system developed by
Marc Cardozo of Tennessee. We are almost finished with building 2- 24x96
greenhouses in which a large pond has been excavated. The pond will be
part tilapia, part spiralina algae culture for the fish to eat. We have
been in contact with NOFA, our local certifying agency, and are helping
them establish organic aquaculture standards. The Tennessee Land Trust has
these standards in place, and if you wish I can send you names and
addresses for them. We hope to be up and running in 2 to 3 weeks. Good
luck in Washington.
----------
From: Deborah J. Brister
To: aquaponics@townsqr.com
Subject: Organic Aquaculture
Date: Friday, May 28, 1999 11:07 AM
Greetings,
I will be traveling to Washington D.C. in a week to present recommendations
to the National Organic Standards Board regarding the proposed organic
aquaculture standards. Before I go, it would be helpful to get an idea of
just how much interest there really is in organic aquaculture. What would
help me is if you can help me identify specific operations that are rearing
fish organically or are attempting to (or would like to) rear them
organically. I would also like to learn more about who else has actually
developed, or is in the process of developing organic standards for
aquaculture. Ted, I know you have written about this in the Aug/Sept issue
of Aquaponics and was wondering if you had any additional information you
would be willing to share as well. Thanks!
Deborah J. Brister
Graduate Research Assistant
Aquaculture and Environmental Policy
Department of Fisheries and Wildlife
University of Minnesota
200 Hodson Hall
1980 Folwell Avenue
St. Paul, MN 55108-6124
----------
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| Message 4 |
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Subject: Re: trout effluent
From: Adriana Gutierrez & Dennis LaGatta
Date: Sat, 29 May 1999 06:30:06 -0400
Andrew,
I think you're back to the various options people use now:
- Gravel beds - Paula and Ted's system
- Perlite beds - my system
- NFT troughs - USDA system
- Floating raft - Jim Rakocy system
- Bag culture - most tomato growers
- Towers - USDA system
- Run to waste
Each has its pros and cons, in part depending on what you're growing. I
think perlite is very, very simple. It's light weight, can be reused
over and over, and can be seeded very densely. In my opinion it's the
best system for greens and herbs. For tomatoes and berries I think bag
culture is the wayto go, using either perlite or pine bark as a growing
media. For full-size heads, if your climate is not too humid, I would
use Jim's floating raft system. He has 1 meter x 100 meter concrete
troughs with 1 foot of water flowing constantly. The lettuces grow in
cups set 7" apart in styrofoam sheets floating on the water. To harvest
they lift the entire sheet out of the water and take it to work tables.
Adriana
"Andrew.D" wrote:
>
> I did receive them thanks Adriana. What I was hoping for was some ideas on
> how the best way to set up with all this waste water as.
>
> I was thinking that the water from the duckpond (300,000L) would be run
> through 100 metres of gravel bed laid into a plastic lined channel.
> Is this the best way? I would love to hear some other ideas.
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| Message 5 |
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Subject: Re: Organic Aquaculture
From: "TGTX"
Date: Sat, 29 May 1999 09:15:03 -0500
There are several points to respond to from various participants, so I will
try to touch on each point
Jim wrote:
>Wendy,
>Why no wild caught fish meal and oil? Isn't it made from fish which
wouldn't be
>utilized otherwise? (humanocentric position;)
>What would you suggest as a replacement? I don't know of _any_ viable
replacement,
>cheap or expensive, organic or otherwise. I've looked..
>and am still looking.
Hi Jim. I do not agree that wild caught fish and fish oil should be
excluded from all organic fish feeds....although I can see that it might not
be a necessary ingredient. There is no logical basis for prohibiting wild
caught fish meal, unless the fish meal and fish oil are contaminated with
excess levels of mercury or the like, or if there is rancidity which will be
toxic or carcinogenic to the fish eating it. Although it would be more
ecologically efficient to use a plant based protein formulation for fish
feed, it is not horrifically "wrong" to use fish meal. We are talking about
degrees of ecological efficiency here. For example, Tilapia diets might
contain anywhere from 5 to 10% fish meal...whereas diets for more
carnivorous species such as salmonids (trout) and centrarchids (bass) may
contain 15 to 30% fish meal. The folks who object to fish meal as an
ingredient (such as the Environmental Defence League )use the arguement that
it is an ecological net "loss" to feed a fish with wild caught fish meal.
Although they may have the right idea or goal, I suggest that the numbers
don't always exactly add up for them, ...try as we might...we cannot always
be "ecologically correct".
If you feed a Tilapia 1.5 lbs of fish feed to acheive 1 lb of fresh Tilapia
flesh, then a 5% fish meal diet means you have used 0.075 lbs of fish meal
grow 1 lb of Tilapia (granted, that is dry weight meal to weight weight fish
flesh...so they have a point, but not a very strong one). The rest of the
feed is usually soy, wheat, corn, and other plant ingredients. To answer
your quest for the plant based diet, Jim, there certainly are all plant
protein formulations that have worked for Tilapia- quite well indeed, and it
is not only an issue of amino acids - such as lysine and methionine that
must be taken into account, but essential fatty acids- soy and corn alone
will not fulfill the essential fatty acid needs of the fish..and just to be
safe, methionine and lysine amino acids are considered needed at trace
levels.
I have worked with Zeigler Brothers in Pennsylvania to come up with a total
organic fish feed diet. I persuaded Zeigler Brothers to become the first
organically certified fish feed mill in the USA, (that I am aware of) but I
had to find them a local distributor of organically certified grains, then I
came up with an all plant protein formulation, which their fish nutritionist
modified somewhat and approved as being able to fullfill the needs of the
fish up to market size and beyond. The diet consists mostly of organic soy.
We would need cooperative purchasing to make the mill a going concern for
organic feed production. The cost has not been worked out yet, until we get
cooperative purchasing agreements in place....There you have it, folks.
Please recall Jim Rackocy's comments on greenwater culture in light of the
organic diet. The single celled microalgae growing in greenwater Tilapia
culture, along with bacterial biomass growing on suspended detrital
material, can provide as much as 50% of the food that the Tilapia will
incorporate into their biomass. This is why some pond research has shown
"impossible" feed conversion results of less than 1 lb of feed for 1 pound
of Tilapia flesh...The added bonus to greenwater culture is that the algae
are producing the essential fatty acids and other substances (such as
carotene pigments, etc) important to Tilapia health, such as EPA
(eicosapentanoic acid) and DHA (dodecahexanoic acid)...also important to OUR
HEALTH, I might add. The bacteria can provide vitamin B12 and other
essential trace nutrients and vitamins, along with bulk nutrition
(carbohydrates, proteins, fats). Tilapia have gill rakers and are quite
good at injesting both pellets and cruising around filter feeding and
snipping off filamentous algae....This is why I like them so much...they are
a lot like me...I'll eat just about anything on the plate, don'cha know.
Next.....about the comment from our friends in upstate New York. You
mentioned that you were working on NOFA organic aquaculture
standards..Perhaps you meant you were working on an amendment to the organic
aquaculture standards for fish?. NOFA already has organic aquaculture
standards. I am holding them in my hand right now. John Reid at
Bioshelters in Amherst, Massachusetts helped them develop those
standards....with great difficulty and delays...something like a dozen years
of effort on his part???? Some of the superstition factors that I discussed
in my last post apparently came into play I guess the traditional organic
farmers on the certification agency's staff, who did not have a clue about
aquaculture, were struggling with aquaculture in ignorance- trying to make
their own paradigm fit into aquaculture standards. In any case, they
finally came up with a set of standards.
Of course I agree completely with Wendy's analysis of micromanagement of
water quality parameters for organic aquaculture. That is why I included
the flexible format in the water quality monitoring section....We must trust
that the the aquaculture farmer has sufficient biological knowledge as to
what will keep her fish, kelp, alligators, snails, tube worms, clams,
microalgae, or bullfrogs not only alive but healthy and thriving....
The USDA should not even be involved in this, but alias and alack, here we
are.
I am on record that I oppose the involvement of the federal government in
National Organic Standards. Nevertheless, back in 1992, the US. Congress
passed the Organic Food Production Act, and launched a very long and
unproductive period before anything was done...and put the responsibility in
the hands of the USDA...possibly one of the most overstaffed and bloated
beauracracies known unto man. Having the USDA in charge of national
organic standards is like unto a monkey and a football engaged in an attempt
to consumate an amorous affair. Reminds me of a cartoon I saw in the
paper one day. One picture of a vast, caverous field of office cubicles
stretching past infinity...past the event horizon...kind of like the last
scene in Raiders of the Lost Ark, except you see office cubicles instead of
shipping crates in a warehouse. The area is labeled USDA offices... You see
a guy up front in one cubicle who is quite distressed, explaning to his
supervisor on the phone that his designated farmer just died.
I would have preferred a private, not-for profit, free enterprise, trade
association or Organic Trade Congress to have been formed by the free
association of stakeholders such as consumer groups, farmers, distributors,
and others....This works for hospitals, engineering societies, industrial
trade groups, retail distributors, chambers of commerce, ASTM.. (the
American Society for Testing and Materials) and others....Why in the world
organic farmers allowed this to happen I will never understand...but here we
are, so we might as well keep the government from going too wacky and too
far...as they seem destined to do by the nature of the beast. Surely we
couldn't as sovereign citizens demand that the act be repealed and cut back
on government involvement and thus do it ourselves...Nah....that would
be...self determination and responsibility...only the federal government
should have that role in the world, Right?
Gotta Go.
Ted
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| Message 6 |
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Subject: Re: Organic Aquaculture
From: Gordon Watkins
Date: Sat, 29 May 1999 10:02:37 -0500
Deborah,
Good to hear that you've discovered the Aquaponic list. Since its
inception there has been much discussion about organic aquaculture in
general and the National Standards in particular, including discussion of
the most recent draft of the aquaculture standards. Lacking a complete
archive of these discussions, perhaps list owner Paula Speraneo has copies
which she can forward to you (sorry to be volunteering you, Paula). You will
see from these discussions that there is quite a bit of interest in organic
fish production and ongoing efforts to develop acceptable feeds.
Good luck in DC.
Gordon Watkins
"Deborah J. Brister" wrote:
> The National Organic Standards Board (NOSB) has been in the process of
defining organic aquaculture using a framework from organic agriculture.
This is and will be an ongoing process.
>
> Professor Anne Kapuscinski, (University of Minnesota) and I have developed
recommendations that pinpoint differences between agriculture and
aquaculture. Our recommendations respond to Organic Aquaculture Standards
Drafts #2 and #3 submitted by the Livestock Committee of NOSB.
>
> These drafts include issues on feed, environment, origin and breeding of
stock, health care, harvesting, siting and general requirements. Our
response to these issues is rather lengthy (14 pages) and is currently in a
format that makes direct reference to the Livestock Committee's drafts 2 and
3. Without these drafts in hand as a reference, reading our
recommendations would be rather confusing. For this reason, we will wait
until after the NOSB meeting to rewrite our document so it is not necessary
to have all of the drafts in hand to follow our chain of thinking and rationale.
>
> If you are interested in reading the NOSB Livestock Committee's drafts
and our recommendations (which will be made publicly available after the
meeting) I strongly urge you to contact the Committee's Chair, Fred
Kirchenmann at farmvo@daktel.com or Mark Keating at
merrigan@access.digex.net . I would also strongly urge you to contact them,
express your interest in organic aquaculture and provide them with
constructive feedback.
>
> As a side note, we have just proposed to the Livestock Committee that we
will convene an informational workshop to discuss organic aquaculture
standards. We hope to involve a variety of participants from all sectors of
the organic farming and aquaculture industry. The outcome of the workshop
would be to stimulate comments on the draft recommendations by late fall of
this year.
>
> I look forward to the ongoing discussions of organic aquaculture and hope
to learn of other growers that are interested in, or are active in this area.
>
> Deborah J. Brister
> Graduate Research Assistant
> Aquaculture and Environmental Policy
> Department of Fisheries and Wildlife
> University of Minnesota
> 200 Hodson Hall
> 1980 Folwell Avenue
> St. Paul, MN 55108-6124
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| Message 7 |
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Subject: Re: Organic Aquaculture
From: Gordon Watkins
Date: Sat, 29 May 1999 10:03:56 -0500
Jim,
Can you be more specific?
Gordon Watkins
"Jim Sealy Jr." wrote:
> Fish meal can be replaced with other protein sources, but
> certain amino acids will be lacking for which there are no good
substitutes, organic
> or otherwise.
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| Message 8 |
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Subject: Re: Organic Aquaculture
From: "Wendy Nagurny"
Date: Sat, 29 May 1999 11:10:58 -0400
Jim,
My reasoning for prohibiting wild caught fish from being used in organic
feeds has nothing to do with utilization/preservation of wild species. It
has to do with the myriad of pollutants that are absorbed and consumed by
these wild species that we have no control over. Many of these undesirable
pollutants are passed down in the food chain by consumption. DDT, PCB's and
mercury are examples. Do we test every fish haul for contaminants that may
be concentrated during processing? I am not nearly so concerned about fish
pulled from waters within the USA and Canada, but processed fish meal and
oils may come from anywhere where there are not so rigid standards on toxic
waste dumping. To me, the most important meaning of "Organic" is "without
toxic waste".
I don't know what would be a direct substitute for fish oil and meal. Can
insect larvae and/or annelids such as earthworms, mealworms, maggots or
other grubs, be substituted in the processing? Both can be raised in great
quantities under organic conditions. I don't know enough about the
nutritional value of the various possibilities to give you a direct answer.
But I do feel that alternatives need to be found -- good economical
alternatives.
Wendy
>Wendy,
>Why no wild caught fish meal and oil? Isn't it made from fish which
wouldn't be
>utilized otherwise? (humanocentric position;)
>What would you suggest as a replacement? I don't know of _any_ viable
replacement,
>cheap or expensive, organic or otherwise. I've looked..
>and am still looking.
>Ji
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| Message 9 |
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Subject: RE: Organic Aquaculture
From: "Ronald W. Brooks"
Date: Sat, 29 May 1999 14:18:18 -0400
Sam
I feed this to the following
Oscar fry , they love it as it moves when sinking
Goldfish fry
Koi fry
I also have feed it to crayfish
Ron
The One Who Walks Two Paths
-> -----Original Message-----
-> From: aquaponics
-> [mailto:aquaponics]On Behalf Of Sam Levy
-> Sent: Saturday, May 29, 1999 4:55 AM
-> To: aquaponics@townsqr.com
-> Subject: RE: Organic Aquaculture
->
->
-> Ron-
->
-> I assume that this is a tilapia feed--have you treid ti w/other fish?
->
-> sam
->
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| Message 10 |
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Subject: Re: Organic Aquaculture
From: "Jim Sealy Jr."
Date: Sat, 29 May 1999 14:03:13 -0500
I was thinking of lysine, but as Ted mentioned, methionine and certain fatty
acids
also come from fishmeal and oil. It was my thought that the fatty acids
could come
from other sources, but lysine is only available economically from wild
caught fish.
Ted: Where do the lysine and fatty acids come from in your feed formulation?
Jim
Gordon Watkins wrote:
>
> Jim,
> Can you be more specific?
> Gordon Watkins
>
> "Jim Sealy Jr." wrote:
>
> > Fish meal can be replaced with other protein sources, but
> > certain amino acids will be lacking for which there are no good
substitutes, organic
> > or otherwise.
> >
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| Message 11 |
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Subject: Re: Organic Aquaculture
From: "TGTX"
Date: Sat, 29 May 1999 14:55:47 -0500
>Ted: Where do the lysine and fatty acids come from in your feed
formulation?
>
>
>Jim
Lysine can come from high lysine corn varieties. Amaranth has a very high
lysine content. Both of these can be grown organically. Yeast and a number
of microorganism can produce lysine in pure form to add as trace amounts in
the feed. Fatty acids are important and were the real trick for a while.
Soy oil is a good start. Corn gluten has been used as a fish meal
substitute. There is another organic grain that gives us the prime fatty
acid profile that we need. That is what makes my formulation (and others
similar to it- mine is not exclusive by any means) work as an all plant
protein substitute. By the way, I am not selling this stuff, I just want to
derive some degree of benefit from the individual work that I did and all
the footwork and independent research I did to make this happen. If others
benefit from it directly or indirectly, then that is great too. I want this
to work for lots and lots of people- especially the hard working fish
farmers out there.
Also, don't forget the green water effect- we don't have to worry if the
pellet does not give us 100% of what the fish need, as long as they have
access to good algae and good bacteria in the culture system to supplement
the diet with natural vitamins etc. That is why I kept harping on the
sprouts idea for organic fish feed supplementation. I went off on that
topic for several weeks, but have not seen a lot of discussion about it
since then.
My last point relates to feed cost. If conventional feed typically costs
around 20 to 25 cents a pound for folks buying 50 lb bags at a time, then
organic feed must have comparable costs because I dont think organic fish
will pull more than about 10 to 15 percent more in price per pound at the
farm gate than conventionally raised farm fish...however, it will likely get
you more of the total market share than you would if you were raising fish
conventionally (that is, not certified organic). I think we need to shoot
for about 15 to 17 cents per pound for feed in bulk quantities (commercial
fish farm volume purchases) to make organic Tilapia farms profitable. That
is my opinion.
Jim Searcy, if your local mill is willing to become certified organic (even
part of the mill will do if you can segregate the ingredients and the
operations- many mills have more than one extruder or pelletizer at each
facility) then we could arrange for the all plant protein formulation to be
made there in Mississippi, at near the price you mentioned for Tilapia feed
earlier (12.5 cents per pound) Again, we would need cooperative bulk
purchasing to make this happen. I am working on getting a feed mill here in
Texas to do the same. In 5 or 10 years, we could have organically certified
fish feed produced in every region of the US.
Ted.
Ted.
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| Message 12 |
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Subject: Re: Organic Aquaculture
From: "Uwe Bruenjes"
Date: Sat, 29 May 99 15:33:23 PDT
Hi Wendy and others,
some time ago there was a discussion about raising grubs and maggots on =
the IBS (integrated bio-systems) list, to which you and probably others =
belong. Maybe producing these critters for their inclusion in fish feed =
could be a very sensible application. Somebody from that list could tell =
us a little more about this culture? And as earthworms could even be rais=
ed on shredded cardboard and paper, this could be another interesting inp=
ut to the fish feed factories.
Uwe
----------
(snip)
> I don't know what would be a direct substitute for fish oil and meal. =
Can
> insect larvae and/or annelids such as earthworms, mealworms, maggots =
or
> other grubs, be substituted in the processing? Both can be raised in =
great
> quantities under organic conditions. I don't know enough about the
> nutritional value of the various possibilities to give you a direct ans=
wer.
> But I do feel that alternatives need to be found -- good economical
> alternatives.
>
> Wendy
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| Message 13 |
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Subject: Re: Organic Aquaculture
From: William Evans
Date: Sat, 29 May 1999 14:40:13 -0700
And as earthworms could even be raised on shredded cardboard and paper,
this could be another interesting input to the fish feed factories.
>
> Uwe
>
> or how about 2 billion tons of organicwaste( from all sources), that is
disposed of yearly(US)
bill evans
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| Message 14 |
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Subject: Re: Organic Aquaculture
From: "Uwe Bruenjes"
Date: Sat, 29 May 99 15:38:39 PDT
Hi Ted,
of all the fish species mentioned on this list, which would be able to =
benefit from green water (tilapia, bream, etc.)?
Uwe
----------
(snip)
> Also, don't forget the green water effect- we don't have to worry if =
the
> pellet does not give us 100% of what the fish need, as long as they hav=
e
> access to good algae and good bacteria in the culture system to supplem=
ent
> the diet with natural vitamins etc. That is why I kept harping on the
> sprouts idea for organic fish feed supplementation. I went off on that
> topic for several weeks, but have not seen a lot of discussion about =
it
> since then.
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| Message 15 |
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Subject: Re: Organic Aquaculture
From: "Uwe Bruenjes"
Date: Sat, 29 May 99 15:48:06 PDT
Hi Bill,
that's right, though many times it's a little tricky to seperate the orga=
nic waste from all the other inorganic stuff.
Uwe
----------
> > or how about 2 billion tons of organicwaste( from all sources), that =
is
> disposed of yearly(US)
> bill evans
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| Message 16 |
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Subject: Re: Organic Aquaculture
From: William Evans
Date: Sat, 29 May 1999 14:58:47 -0700
Uwe Bruenjes wrote:
>
> Hi Bill,
>
> that's right, though many times it's a little tricky to seperate the
organic waste from all the other inorganic stuff.
> not to mention, getting the existing (and growing, IMHO) cadre of green
waste facilities to vermicompost their compost.
> Uwe
>
> ----------
>
> > > or how about 2 billion tons of organicwaste( from all sources), that is
> > disposed of yearly(US)
> > bill evans
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| Message 17 |
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Subject: Re: Questions - Reposting
From: "Clark Allison"
Date: Sat, 29 May 1999 15:11:33 PDT
Paula wrote:
>Would you repost your questions?
>
>I'd be happy to take a stab at any I can help with.
>
>Paula
>S&S Aqua Farm, 8386 County Road 8820, West Plains, MO 65775 417-256-5124
Sure. This is from a hobbyist perspective. Are there fish that are
particularly good at eating the floating algae commonly found in outdoor
ponds? I live in Kentucky and would be especially interested in fish that
would be adapted to this area, climate, etc.
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
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| Message 18 |
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Subject: Re: Organic Aquaculture
From: "TGTX"
Date: Sat, 29 May 1999 18:42:46 -0500
>Hi Ted,
>of all the fish species mentioned on this list, which would be able to
benefit from green >water (tilapia, bream, etc.)?
>Uwe
Uwe, I think all species could benefit from properly managed and controlled
greenwater systems, but I think the benefit profile might differ for
different species, depending on their position in natural food webs.
All of the species would benefit from nitrogenous waste control. If you
think about it, photosynthetic organisms combined with heterotrophic
bacteria can be more reliable and more thorough at nitrogenous waste removal
than our bacterial buddies, Nitrosomonas and Nitrobacter acting alone in a
"traditional" biofilter, since algae (in the case of algal turf scrubbers
and in green water culture) and vascular plants (in the case of aquaponics
and constructed wetland systems) can assimilate and biosynthesize all forms
of inorganic nitrogen (NH4, NO2, and NO3) into their biomass. The more
nitrate that our plant buddies take up, the more efficient our bacterial
buddies can convert ammonia to nitrite and nitrite to nitrate. The plants
can take up all 3 forms, so there is some competion for the nitrogen among
the critters. Even heterotrophic bacteria that are growing in systems with
higher C:N ratio waters can assimilate NH4 to use it as their protein
biosynthesis.
The different benefits to the various fish species we have talked about
culturing would depend on that species ability to filter feed and derive
nutrition from the algae/heterotrophic bacteria in suspension. Obviously
some of the Tilapia can filter feed. The centrarchids (bream..sunfish..bass
and others) might benefit from green water culture indirectly from a
nutritional standpoint from the fact that the green water would support
zooplankters which the young centrarchids would prey upon. But the green
water can get too thick and kill everything if you are not careful.
In any case, the green water culture needs lots of oxygen...Never let it go
down below 3 ppm or you are in trouble. It needs to have just enough algae
and bacteria that biochemical oxygen demand does not approach hypereutrophic
levels. The key to that appears to be in managing the protein content of
the feed pellets. If the feed is reduced from 32-35 % protein to 20-28%
protein, then the higher C to N ratio may support a better
algal/heterotrophic bacteria population for Tilapia. I dont know if the
lower protein feed would benefit the centrarchids, however. It seems the
best candidate for greenwater culture would be Tilapia...carp...maybe
paddlefish...who knows?
I would encourage anyone to investigate this. The Israelis have done some
work in this area in Tilapia ponds, with interesting results. Jim Rakocy
could probably tell us a lot more on the pragmatic side of this.
Hope this helps.
Ted.
S&S Aqua Farm, 8386 County Road 8820, West Plains, MO 65775 417-256-5124
Web page http://www.townsqr.com/snsaqua/
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