Aquaponics Digest - Fri 01/15/99
Message 1: Greenwater tank culture
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 2: Re: Greenwater tank culture
from "Jim Sealy Jr."
Message 3: Re: Greenwater tank culture
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 4: Re: worms
from Gordon Watkins
Message 5: Re: Greenwater tank culture
from doelle
Message 6: Re: Greenwater tank culture
from John Shannonhouse
Message 7: Re: Greenwater tank culture
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 8: Re: Greenwater tank culture
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 9: Re: Tomato Varieties
from "John Phillips"
Message 10: Re: Tomato Varieties
from William Evans
Message 11: Re: Tomato Varieties
from Michael Strates
Message 12: Re: Tomato Varieties
from William Evans
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Subject: Greenwater tank culture
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Fri, 15 Jan 1999 10:45:18 -0400 (AST)
We just harvested a small trial using a technology called greenwater tank
culture. This is not aquaponics per se, but in greenwater tank culture we
use a clarifier to remove feces, detritus and dead algal cells twice daily.
This wastewater goes to a sump and from there it is used to irrigate and
fertilize field crops. The organic matter also improves soil structure and
releases nutrients slowly so there is a residual effect long after
irrigation stops. We are currently producing forage for livestock, but in
the past we raised bell peppers and pak choi. What's exciting about this
technology is its simplicity and its improvement over pond culture. In a
20-ft tank (water depth -3.5 ft.), we harvested 1,164 lbs. of Nile tilapia.
The average weight was 1,002 g (2.21 lbs.). We are growing our fish large
for the fillet market. A fish this size will yield two 6-oz fillets. Well
managed ponds will produce a final density of 0.5 kg/m3. Our final density
was 17.0 kg/m3 (0.14 lbs./gallon) or 34 times better than pond culture. The
reason: Ponds must treat their own waste which limits daily feed input to
about 100 lbs./acre with some nighttime aeration. It's an algal-based system
and algae are unstable, going through many population successions and
occasional die-offs, which leads to fish kills if the pond isn't aerated.
There's plenty of algae in greenwater tank culture, as the name implies, but
it is really a bacterial-based system, which makes it more stable.
Continuous aeration in greenwater tanks keeps much of the organic matter and
associated microorganisms in suspension. Nitrification therefore takes place
in the water column in a process similar to activated sludge treatment, but
with much lower organic loading rates. Excess organic matter and dead algal
cells are removed by the clarifier. Removal of this organic waste lowers
the oxygen demand and the secondary production of ammonia. As a result, our
average feeding rate was equivalent to 1,400 lbs./acre/day. During the
25-week culture period, we removed 17.1 m3 (4,520 gallons) of sludge. The
rearing tank volume was 8,190 gallons. The feed conversion ratio was 1.87.
Feed conversion increases as fish get larger since more of the feed must go
to maintenance rather than growth. With pelleted feed alone the FCR would
have been higher, but in greenwater tilapia receive considerable nutrition
from the algae and bacteria. Unfed fish in the clarifier grew at a rate of 1
g/day compared to 4.7 g/day for the fed fish. Greenwater tank culture is
primarily suited for hardy fish such as tilapia. Next year we plan to build
a tank 7 times larger to see if these results hold at a commercial scale
(for the Virgin Islands). Jim R.
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Subject: Re: Greenwater tank culture
From: "Jim Sealy Jr."
Date: Fri, 15 Jan 1999 09:34:19 -0600
Are you using raft cultured lettuce in the greenwater tank? If not,
why?
Also, I'm considering the possibility of dual cropping one of my
smaller catfish ponds (2.5 acres) this summer and wondered what your
thoughts were on this.
We've completed our managed wetland (200 acres) which will contain
run-off from the big catfish ponds and I'm watching for any other
similar projects so really appreciate seeing this post of yours about
a more intensive version.
Thanks for _all_ your other good posts, too. I've learned a lot from
them and hope to start raft culture here soon as a result of your
posts.
Jim Sealy Jr.
James Rakocy, Ph.D. wrote:
>
> We just harvested a small trial using a technology called greenwater tank
> culture. This is not aquaponics per se, but in greenwater tank culture we
> use a clarifier to remove feces, detritus and dead algal cells twice daily.
>
Jim R.
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Subject: Re: Greenwater tank culture
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Fri, 15 Jan 1999 11:49:15 -0400 (AST)
Jim, Actually in greenwater tank culture nutrients do get high enough for
raft hydroponics, but I would not recommend it. You want the entire surface
area to be exposed to sunlight to grow algae. Also, since suspended soilds
levels are fairly high, the roots would be coated with algae and detritus
with rafts and NFT. With gravel it would clog. Catfish also are probably not
suitable for greenwater systems. Suspended growth nitrification is not as
stable as fixed-film nitrification, and temorarily poor water quality, which
would not seriously affect tilapia, would stress or even kill catfish. Now
clarius, if they were legal, would do great. Carp and maybe pacu might also
do well. Any pond would have to be round and lined with a central drain for
solids removal. Jim R.
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Subject: Re: worms
From: Gordon Watkins
Date: Fri, 15 Jan 1999 10:26:33 -0600
Ted,
According to the literature that came with one of my bins, the ideal C:N
ratio is 30:1. Shredded corrugated cardboard is superior to shredded paper as a
food source for worms due to the animal-based glue which provides N. I soak it
overnight before adding it to the bin. Be careful about using unshredded paper
or cardboard as it will mat down and become anaerobic.
An excellent source of info is the Vermicomposting Forum,
http://www.oldgrowth.org/compost/forum_vermi/ which has an extensive,
searchable archives.
My small indoor bin and large outdoor one are perking right along and
beginning to supply enough worms to feed both my tilapia broodstock as well as
the frogs I'm acclimating before I release them for slug control.
Gordon
Ted Ground wrote:
>
>
> Gotta question or two for you. I have a source of plain corrugated
> cardboard scrap material- no ink or adhesives that I know of. Now my
> question is, the worms will obviously eat this fiberous carbon source just
> like newspaper, right?, But what about the nitrogen? What ratio of carbon
> to nitrogen do I need to feed them? Do you have any solid numbers on C/N
> ratios or just some rules of thumb, feed recipes, etc?
> So many pounds of cardboard to so many pounds of....what? I am also
> interested in any information that anyone out there may have on HUFAs,
> PUFAs, and EFAs (info about various classes of fatty acids) that earthworm
> biomass offers as a fish feed source....
>
>
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Subject: Re: Greenwater tank culture
From: doelle
Date: Sat, 16 Jan 1999 06:59:58 +1100
James,
As exciting and simple the technique sounds and however successful the
feeding and everything else is, YOU ARE RECYCLING PATHOGENS. In our times
today we have to be extremely careful with such recycling because of the
ever increasing antibiotic resistancy, I am not a scaremonger but I have
seen to problems and results of such recycling and can only warn. Whatever
you do with feces from whatever source, use a microbiological test. I just
corrected a paper whereby the microbiology of oysters in oyter farms near
human settlements had been studied. Scary to see the figures of Vibrio
parahaemolyticus, coliforms etc etc in these oysters. These studies were
carried out because of seafood poisining in that area.
The source is the release of human and animal waste into the agricultural
and waterways. Of course, the farms have now to clean up their act.
Why do we always wait till something happens when we now it will happen
eventually >?
Best regards
Horst Doelle
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Subject: Re: Greenwater tank culture
From: John Shannonhouse
Date: Fri, 15 Jan 1999 14:47:05 -0600
Hello,
When more feed is going to maitenence than growth in a large fish
relative to a small fish, does the feed need the same amount of protein as
a percentage of total feed weight in order to maintain optimal growth rate?
It seems to me that a large fish mostly needs extra calories rather than
extra protein in order to maintain its metabolism. Calories could be
provided by bulking up the feeds with extra carbohydrates or a low-qualtiy
protein feed. That should save money, if it works.
John Shannonhouse
Department of Genetics
University of Wisconsin-Madison
jlshanno@students.wisc.edu
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Subject: Re: Greenwater tank culture
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Fri, 15 Jan 1999 17:25:52 -0400 (AST)
That seems logical and usually smaller fish get feed formulations with
higher protein levels. I could envision switching to a lower protein diet in
the later stages. We use 32% protein. There may be a 28% protein feed.
Ahhhh, so many experiments to do and so little time. Jim R.
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Subject: Re: Greenwater tank culture
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Fri, 15 Jan 1999 17:41:45 -0400 (AST)
>James,
>As exciting and simple the technique sounds and however successful the
feeding and everything else is, YOU ARE RECYCLING PATHOGENS. In our times
today we have to be extremely careful with such recycling because of the
ever increasing antibiotic resistancy, I am not a scaremonger but I have
seen to problems and results of such recycling and can only warn. Whatever
you do with feces from whatever source, use a microbiological test. I just
corrected a paper whereby the microbiology of oysters in oyter farms near
human settlements had been studied. Scary to see the figures of Vibrio
parahaemolyticus, coliforms etc etc in these oysters. These studies were
carried out because of seafood poisining in that area.
I don't think so. We use well water, healthy fish, and corn, soybean and
fish meal feed in a closed system. This is not an estuary surrounded by
human settlements inhabited by some sick people. It's a clean, well-aerated
tank in the middle of a field exposed to intense tropical sun and covered by
netting to keep out birds. But we've had this conversation before. Jim R.
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Subject: Re: Tomato Varieties
From: "John Phillips"
Date: Fri, 15 Jan 1999 21:23:05 -0000
Gordon,
Last April you posted some preliminary results with some tomato varieties
you were growing, and noted problems with flavor. Recently, I ordered
quantities of these seeds and I was wondering if your later experience with
the varieties mentioned here produced better tasting fruit. Any update
appreciated, and any suggestions from the list of varieties suitable to hot
climates like Arizona also appreciated. I'm intending to grow these
tomatoes in greenhouses, hopefully with an aquaponics nutrient system
backed up by earthworm leachate.
Thanks,
John Phillips
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Subject: Re: Tomato Varieties
From: William Evans
Date: Fri, 15 Jan 1999 20:49:44 -0800
Pedigree doesnt matter as much as the soil the plant is grown in .A
great tasting tomato variety in one soil can taste horrible in another.
Speaking of hydroponics, has anyone tried using lava gravel in their
system?Being porous, and having some degree of CEC, I would think that
it would be better than most.
billevans
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Subject: Re: Tomato Varieties
From: Michael Strates
Date: Sat, 16 Jan 1999 15:58:20 +1100 (EST)
On Fri, 15 Jan 1999, William Evans wrote:
WE> Speaking of hydroponics, has anyone tried using lava gravel in their
WE> system?Being porous, and having some degree of CEC, I would think that
WE> it would be better than most.
One of my growbeds uses scoria (red porous rock). It works about the same
as perlite, but is a heck of alot heavier.
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Subject: Re: Tomato Varieties
From: William Evans
Date: Fri, 15 Jan 1999 21:04:10 -0800
Yes but perlite is basically silica,whereas the scoria has many
elements?, true?, tho will take forever to turn into clay?Yes it is
heavy, have 20 ton in front yard.
>
> One of my growbeds uses scoria (red porous rock). It works about the same
> as perlite, but is a heck of alot heavier.
>
>
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