Aquaponics Digest - Wed 01/21/98
Message 1: Spirulina, etc
from Gordon Watkins
Message 2: feed, sand aquaponics
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 3: Spirulina
from Gordon Watkins
Message 4: Re: feed, sand aquaponics
from Gordon Watkins
Message 5: Re: feed, sand aquaponics
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 6: Papers from James Rabocy
from PeterJTheisen@eaton.com
Message 7: Re: Papers from James Rabocy
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 8: Re: feed, sand aquaponics
from Gordon Watkins
Message 9: Re: Papers from James Rabocy
from John Shannonhouse
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Subject: Spirulina, etc
From: Gordon Watkins
Date: Wed, 21 Jan 1998 07:56:42 -0600
Hello Jim, and welcome to the list. I'm excited to see you participating
as your many writings have been a great help to me in setting up my
aquaponic system. Mine is based on the IAVS system at NC State and I
woould particularly appreciate it, if you come across any new
information floating around the academic circles, you could pass it on.
The spirulina discussion was in part stimulated by an interest in
finding a vegetable-based protein alternative to fish meal for tilapia
feed. From a practical, economic standpoint it sounds like spirulina is
prohibitively expensive. Do you know of any other suitable substitutes?
Thanks,
Gordon
James Rakocy, Ph.D. wrote:
>
> Hi, I'm new to the group. Just some short responses to Paula and Ted.
> Spirula may be a good food additive but it is also very expensive. Spirulina
> farms dry and encapsulate it and sell spirulina as health food. The price
> per kg is many times greater than fish meal and so it would not be
> economiclly feasible for food fish feed, already a major production cost,
> but it may be economically feasible as aquaria feed for expensive and
> colorful ornamentals.
>
> In aquaponics all available surface area should be devoted to high value
> plant production (lettuce, herbs, etc.). This is critical to turn a profit,
> especially in environmently controlled greenhouses. Although algae is a good
> food for herbivorous/omnivorous fish, it is more than 95% water. It is
> economically better to feed a concentrated, dry (<10% water), complete
> (contains all necessary vitamins and minerals) diet and let the hydroponic
> plants contribute to wastewater treatment, as they remove nutrients even
> faster than algal turf, the rate of uptake depending on the type of
> vegetable, herb, etc.
>
> Jim R.
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Subject: feed, sand aquaponics
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Wed, 21 Jan 1998 11:14:32 -0400 (AST)
Hello Gordon, Finding a suitable vegetable-based food is important in
aquaponics to reduce sodium accumulation, due mainly to the sodium
associated with the fish meal component. I think this feed will be based on
soybean protein. Some work has been done in this area, but it's important
with any new feed not to sacrifice fish health or growth. Most likely, fish
meal protein could be reduced but not eliminated. I'm interested in how your
system performs over the long term. I always thought that sand could clog.
In my system, after removal of all the solids, there's still so much
dissolved organic matter that biological growth partially clogs 4 inch pipes
with a flow rate of 33 gpm. Another problem with the design is the periodic
water exchange in the rearing tank, which is not conducive to high fish
loading, since fish constantly give off waste metabolites. Yesterday we
harvested 921 lbs. of tilapia from an 8-ft. diameter tank. This productivity
level requires constant and rapid water exchange. Jim R. P.S. We have some
new publications.
>Hello Jim, and welcome to the list. I'm excited to see you participating
>as your many writings have been a great help to me in setting up my
>aquaponic system. Mine is based on the IAVS system at NC State and I
>woould particularly appreciate it, if you come across any new
>information floating around the academic circles, you could pass it on.
> The spirulina discussion was in part stimulated by an interest in
>finding a vegetable-based protein alternative to fish meal for tilapia
>feed. From a practical, economic standpoint it sounds like spirulina is
>prohibitively expensive. Do you know of any other suitable substitutes?
> Thanks,
> Gordon
>
>James Rakocy, Ph.D. wrote:
>>
>> Hi, I'm new to the group. Just some short responses to Paula and Ted.
>> Spirula may be a good food additive but it is also very expensive. Spirulina
>> farms dry and encapsulate it and sell spirulina as health food. The price
>> per kg is many times greater than fish meal and so it would not be
>> economiclly feasible for food fish feed, already a major production cost,
>> but it may be economically feasible as aquaria feed for expensive and
>> colorful ornamentals.
>>
>> In aquaponics all available surface area should be devoted to high value
>> plant production (lettuce, herbs, etc.). This is critical to turn a profit,
>> especially in environmently controlled greenhouses. Although algae is a good
>> food for herbivorous/omnivorous fish, it is more than 95% water. It is
>> economically better to feed a concentrated, dry (<10% water), complete
>> (contains all necessary vitamins and minerals) diet and let the hydroponic
>> plants contribute to wastewater treatment, as they remove nutrients even
>> faster than algal turf, the rate of uptake depending on the type of
>> vegetable, herb, etc.
>>
>> Jim R.
>
>
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Subject: Spirulina
From: Gordon Watkins
Date: Wed, 21 Jan 1998 13:03:07 -0600
Paula,
I forwarded your questions on spirulina on to a fish nutritionist who
provided the following response:
Gordon
> 1) Ask the company for a list of publications (or citations) suppporting
> their claims for Spirulina -
> I'll see if I can locate some of them here (articles in major aquaculture
> journals such as "Journal of the world aquaculture society", or "Aquaculture"
> would be easiest to find). The attributes claimed by the company are not
> stated relative to any specific type of feedstuff or diet (Spirulina
> improves survival rate... (relative to what?). A scientific assessment of
> the nutritional value of Spirulina should include such comparisons.
>
> 2. Ask for analytical information on the nutrient content of Spirulina. With
> quantitative information you can compare the value of Spirulina as a nutrient
> source to other sources more typically used in foodfish diets (I have
published
> values for all of the standard feedstuffs). At a minimum you should ask for
> data on the amounts and types of amino acids present in Spirulina. With the
> amino acid profile you can speculate on its value as a protein source.
>
> 3. What level of inclusion does the company recommend that you use if you
> are replacing Fish meal with Spirulina? A high level may cause discoloration
> of the flesh of the Tilapia (a greenish color). Corn products are limited in
> catfish feeds for the same reason (it causes an undesirable yellow color).
>
> 4. Perhaps I should have mentioned this first- I would be surprised if
> Spirulina was less expensive than fish meal - it is highly valued as health
> food for humans which probably makes it prohibitively expensive for use in
> fish feeds (except for ornamental fish). Even if Spirulina is a great protein
> source for Tilapia will your market pay enough for your product to offset the
> added cost of the feed?
>
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Subject: Re: feed, sand aquaponics
From: Gordon Watkins
Date: Wed, 21 Jan 1998 13:48:53 -0600
Hello Jim,
I wasn't aware of the potential problems with sodium buildup due to
fishmeal. Thanks for the alert. Incidentally, are you aware of any cases
of disease in recirculating systems which were tranmitted through
fishmeal? I have some concern, perhaps unfounded, about re-feeding
processed offal to the same family of animals. It seems possible that
certain fish diseases, viruses in particular, could survive processing
and be tranferred via the feed to impact the fish to which it is fed. It
is suspected, for example, that Creutzfield-Jacobs Disease, a human
version of Bovine Spongiform Encephalitis, can be transmitted through
bone meal derived from infected cattle. Do you think this is a
legitimate concern?
Regarding my system, I'm not using fine sand, but a fairly coarse
sand/gravel mixture. On the recommendation of Doug Sanders at NC State,
I use a mixture which will allow 1 inch of water to drain through 12
inches of media in 20 minutes. He indicated that a system using #2
Highway Grade sand, similar in perc rate to what I'm using, had been in
operation for over 5 years with no clogging. My system just became
operational about 3 months ago, and I'm not stocked to capacity yet but
I don't see any clogging so far.
I use submersible pumps on a timer which activates them for 30 minutes
every 1.5 hours during the day (10x/day), which gives me about 5
turnovers per day, probably much less than what you are using, but I
plan to play with this variable quite a bit as my stocking rates and
plant densities increase. The yield you mention is impressive. Can you
describe the system in more detail?
What I'm shooting for is not maximum yield, but optimum yield, and I've
opted for a relatively low-tech system with a high output-to-input
ratio.
I built my small, 300 sq ft system to test the IAVS design's
feasibility for expansion to a commercial scale so I welcome any
questions, comments, criticisms you or anyone may have about the IAVS
design. My hope is to test it rigorously and thoroughly and I welcome
input from all quarters.
How can I get more information on the publications you mention?
Best regards,
Gordon
James Rakocy, Ph.D. wrote:
>
> Hello Gordon, Finding a suitable vegetable-based food is important in
> aquaponics to reduce sodium accumulation, due mainly to the sodium
> associated with the fish meal component. I think this feed will be based on
> soybean protein. Some work has been done in this area, but it's important
> with any new feed not to sacrifice fish health or growth. Most likely, fish
> meal protein could be reduced but not eliminated. I'm interested in how your
> system performs over the long term. I always thought that sand could clog.
> In my system, after removal of all the solids, there's still so much
> dissolved organic matter that biological growth partially clogs 4 inch pipes
> with a flow rate of 33 gpm. Another problem with the design is the periodic
> water exchange in the rearing tank, which is not conducive to high fish
> loading, since fish constantly give off waste metabolites. Yesterday we
> harvested 921 lbs. of tilapia from an 8-ft. diameter tank. This productivity
> level requires constant and rapid water exchange. Jim R. P.S. We have some
> new publications.
>
>
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Subject: Re: feed, sand aquaponics
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Wed, 21 Jan 1998 16:42:42 -0400 (AST)
>Hello Jim,
> I wasn't aware of the potential problems with sodium buildup due to
>fishmeal. Thanks for the alert. Incidentally, are you aware of any cases
>of disease in recirculating systems which were tranmitted through
>fishmeal? I have some concern, perhaps unfounded, about re-feeding
>processed offal to the same family of animals. It seems possible that
>certain fish diseases, viruses in particular, could survive processing
>and be tranferred via the feed to impact the fish to which it is fed. It
>is suspected, for example, that Creutzfield-Jacobs Disease, a human
>version of Bovine Spongiform Encephalitis, can be transmitted through
>bone meal derived from infected cattle. Do you think this is a
>legitimate concern?
I don't know, but I doubt it. If there was a problem, it should have
surfaced by now.
> Regarding my system, I'm not using fine sand, but a fairly coarse
>sand/gravel mixture. On the recommendation of Doug Sanders at NC State,
>I use a mixture which will allow 1 inch of water to drain through 12
>inches of media in 20 minutes. He indicated that a system using #2
>Highway Grade sand, similar in perc rate to what I'm using, had been in
>operation for over 5 years with no clogging. My system just became
>operational about 3 months ago, and I'm not stocked to capacity yet but
>I don't see any clogging so far.
There are many factors to consider, but loading rate (amount of daily feed
input) is probably the most important followed by daily water exchange rate.
A lightly loaded system with a large biofilter may not clog. Let me know
what happens.
> I use submersible pumps on a timer which activates them for 30 minutes
>every 1.5 hours during the day (10x/day), which gives me about 5
>turnovers per day, probably much less than what you are using, but I
>plan to play with this variable quite a bit as my stocking rates and
>plant densities increase. The yield you mention is impressive. Can you
>describe the system in more detail?
The average retention time in our tanks is 48 min; that's 30 turnovers/day.
Plus there's heavy aeration. There's two papers published in the proceedings
of the recent tilapia conference in Orlando plus one paper in the new book,
Tilapia Aquaculture in the Americas. I'll send the papers if you give me
your address.
> What I'm shooting for is not maximum yield, but optimum yield, and I've
>opted for a relatively low-tech system with a high output-to-input
>ratio.
We are shooting for maximum profit on a commercial level and our system
relative to indoor recirc systems is low tech, what is called appropriate or
intermediate technology for tropical islands.
> I built my small, 300 sq ft system to test the IAVS design's
>feasibility for expansion to a commercial scale so I welcome any
>questions, comments, criticisms you or anyone may have about the IAVS
>design. My hope is to test it rigorously and thoroughly and I welcome
>input from all quarters.
The paper quantifies our system so you should compare your production levels
with ours. Use unit measures (lb/ft2, lb/gallon) to quantify inputs and
outputs.
> How can I get more information on the publications you mention?
>
> Best regards,
> Gordon
>
>
>James Rakocy, Ph.D. wrote:
>>
>> Hello Gordon, Finding a suitable vegetable-based food is important in
>> aquaponics to reduce sodium accumulation, due mainly to the sodium
>> associated with the fish meal component. I think this feed will be based on
>> soybean protein. Some work has been done in this area, but it's important
>> with any new feed not to sacrifice fish health or growth. Most likely, fish
>> meal protein could be reduced but not eliminated. I'm interested in how your
>> system performs over the long term. I always thought that sand could clog.
>> In my system, after removal of all the solids, there's still so much
>> dissolved organic matter that biological growth partially clogs 4 inch pipes
>> with a flow rate of 33 gpm. Another problem with the design is the periodic
>> water exchange in the rearing tank, which is not conducive to high fish
>> loading, since fish constantly give off waste metabolites. Yesterday we
>> harvested 921 lbs. of tilapia from an 8-ft. diameter tank. This productivity
>> level requires constant and rapid water exchange. Jim R. P.S. We have some
>> new publications.
>>
>>
>
>
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Subject: Papers from James Rabocy
From: PeterJTheisen@eaton.com
Date: 21 Jan 98 15:57:37 EST
If I understand the last post, James, you will be sending Gordon some
information on recent studies of a certain Aquaponics system. Can you
post or attach these papers for all of us? Or can I get a copy? As to not
overburden you with postage I would be gald to send you a self addressed
envelop if you give me your address.
Thank you
Pete T.
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Subject: Re: Papers from James Rabocy
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Wed, 21 Jan 1998 17:15:17 -0400 (AST)
Postage is no problem, but if you want to contact me off the net, you can
reach me at 340-692-4031 or University of the Virgin Islands, Agricultural
Experiment Station, RR 2, Box 10,000, Kingshill, VI 00850.
>If I understand the last post, James, you will be sending Gordon some
>information on recent studies of a certain Aquaponics system. Can you
>post or attach these papers for all of us? Or can I get a copy? As to not
>overburden you with postage I would be gald to send you a self addressed
>envelop if you give me your address.
>
>Thank you
>Pete T.
>
>
>
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Subject: Re: feed, sand aquaponics
From: Gordon Watkins
Date: Wed, 21 Jan 1998 18:09:18 -0600
Hello Jim,
Thanks for your kind offer. My mailing address is:
Gordon Watkins
HCR 72 Box 34
Parthenon, AR 72666
James Rakocy, Ph.D. wrote:
>
> There's two papers published in the proceedings
> of the recent tilapia conference in Orlando plus one paper in the new book,
> Tilapia Aquaculture in the Americas. I'll send the papers if you give me
> your address.
>
> >
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Subject: Re: Papers from James Rabocy
From: John Shannonhouse
Date: Wed, 21 Jan 1998 21:42:08 -0600
Hello,
I looked on Medline (which has abstracts from papers relating to a
variety of biological subjects including aquaculture) and could not find
any papers by Rabocy or Rakocy. It is probably not the best database for a
search, though. Are you willing to post the journal, vol #, date, etc. for
your papers so I can look them up?
John Shannonhouse
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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