Aquaponics Digest - Thu 03/23/00
Message 1: Re: Any suggestions
from "Sam Levy"
Message 2: Re: Duckweed Chronicles
from "Sam Levy"
Message 3: Re: What do fish eat?
from "Sam Levy"
Message 4: Re: Bolting lettuce
from Donald Bailey
Message 5: Re: revove from list
from "Mike Ross"
Message 6: FW: USDA Organic Aquatic Hearings
from "Ron Brooks"
Message 7: on vacation until may 9
from wills/nachreiner
Message 8: nitrite uptake
from laberge@cil.qc.ca (LABERGE MARC)
Message 9: Re: Any suggestions
from "Barry Thomas"
Message 10: Re: Any suggestions
from "James Rakocy"
Message 11: Re: Any suggestions
from "Barry Thomas"
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| Message 1 |
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Subject: Re: Any suggestions
From: "Sam Levy"
Date: Thu, 23 Mar 2000 02:14:00 PST
>
>
>I suppose that anything you place in the tank will foul over time but
>vertical dividers wouldn't have that large a surface area and shouldn't
>interfere too much with cleaning?
>
>Barry
barry,
all depends what you need to do--i've found fold up floating net cages to be
a great solution for all sorts of ad-hoc situations--there's a smal group
after grading, there's some fish you want to keep an eye on, &c. on the
other hand, i've never seen a movable divider that actually kept the fish
from moving between the groups.
but to each his own.
sam
>
>
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| Message 2 |
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Subject: Re: Duckweed Chronicles
From: "Sam Levy"
Date: Thu, 23 Mar 2000 02:16:08 PST
ted,
thanks again and i guess i'll have to ask about a "c" element next time.
sam
>
>Sam, we should acknowledge those who think this is a boron topic, and
>then...let's just go ahead and talk about it anyway.
>
>
>
>Shalom!
>
>Ted
>
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Subject: Re: What do fish eat?
From: "Sam Levy"
Date: Thu, 23 Mar 2000 02:21:01 PST
carolyn,
you might have a look at:
aquaculture source book (a guide to north american species)
iversen, edwin & hale, kay
published by avi books
sam
>
>
>Is there a common desk reference that shows which fish or minnow species
>are
>vegetarian, predators, omnivores?
>
>Thanks,
>Carolyn
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Subject: Re: Bolting lettuce
From: Donald Bailey
Date: Thu, 23 Mar 2000 09:29:09 -0400
At the University of the Virgin Islands we have tested many varieties in
our aquaponic system. The head types often look beautiful on the
outside but are rotted at the core, probably due to heat and moisture in
the closed leaves. Montello is one variety that did form a head in our
'winter' temperatures and stayed open in the summer. Our main lettuce
crops are Sierra, a red leaf, Nevada, a green leaf, and Parris Island
(winter) and Kalura (summer) the romaine varieties.
We built evaporative coolers to test cooling the water in the
summertime. They are 30" wide x 29"deep x 48" high blocks of plastic
cooling tower media enclosed in a plywood box 30" x 72" x 48". the
media is at one end of the box and a fan is at the other. Water
trickles down through the media and air is pulled through the media by
the fan cooling the water. We only operate this at night, when the
temperature and humidity are right for operation. We can cool the water
by about 3 degrees C with this method. We have not yet determined
electric costs of the fan operation nor the cost of reduced fish
production (slower growth rate in the colder water). Those costs might
all get offset but more lettuce production. This summer's experiments
will start in May and we should have some feel for chilling/cooling
success by the time of our Short Course at the end of June.
Don Bailey
http://rps.uvi.edu/AES/Aquaculture/aqua.html
> Subject: Bolting Lettuce
> From: Tony Cooper
> Date: Wed, 22 Mar 2000 22:06:53 -0800
>
> Does anyone living in a hot climate [e.g. William in Hawaii] have any
> recommendations for slow bolting lettuce varieties?
>
> I want to grow lettuce in aquaponics with a good tight head which is the
> preferred type in the market here.
> Daytime temps get up to 35C.
>
> Also does anyone have a home made water cooling solution? I am thinking
> of running the water through a coil of plastic tube placed inside a
> water filled chest freezer placed just before it enters the growing
> channels.
>
> Thoughts anyone?
>
> Tony Cooper.
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Subject: Re: revove from list
From: "Mike Ross"
Date: Thu, 23 Mar 2000 08:00:06 -0600
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Subject: FW: USDA Organic Aquatic Hearings
From: "Ron Brooks"
Date: Thu, 23 Mar 2000 10:41:56 -0500
Laura sent me this this morning and though tit would be of interest to the
list
Ron
-----Original Message-----
From: Ohio aquaculture people [mailto:aqua-ohio@ag.ohio-state.edu]On
Behalf Of Laura Tiu
Sent: Thursday, March 23, 2000 9:50 AM
To: Ohio aquaculture people
Subject: Fwd: USDA Organic Aquatic Hearings
>
>Please distribute the following news release from USDA-AMS to others who
may
>have an interest in participating in one of three public meetings planned
to
>discuss organic standards specific to aquatic animals.
>
>Gary Jensen
>USDA-CSREES
>_____________________________________________________________
>
> Below is a copy of a news release regarding public hearings for
> organic standards for aquaculture which the Agricultural Marketing
> Service will be holding. Please pass this along to anyone you might
> know who is interested in organic standards for this industry.
>
> Regards,
>
> Lisa M. Twedt
> Agricultural Marketing Specialist
> Forest and Fishery Products Division
>
> USDA SETS MEETINGS ON ORGANIC PRODUCTION, HANDLING OF AQUATIC
> ANIMALS
>
> WASHINGTON, March, 20, 2000 The U.S. Department of Agriculture
> will convene three public meetings to discuss the production and
> handling of aquatic animals to be labeled as "organic." Meetings will
> be held on April 10 at the Mobile Convention Center in Mobile, Ala;
> April 12 at the Anchorage Hilton in Anchorage, Alaska; and May 3 at
> the Providence Biltmore in Providence, R.I. Public comments on this
> issue are also requested.
>
> "We are conducting these meetings as an outgrowth of our new
> proposal for uniform and consistent national standards for organic
> food. The meetings will help us gather input to develop acquatic
> standards," said Kathleen Merrigan, administrator of USDA's
> Agricultural Marketing Service. The Organic Foods Production Act of
> 1990 was designed to establish national standards governing the
> marketing of certain agricultural products as organically produced
> products, assure consumers that organically produced products meet a
> consistent standard, and facilitate commerce in fresh and processed
> food that is organically produced. AMS' National Organic Program was
> created to implement the provisions of the act.
>
> Federal entities that share regulatory authority over the
> production and marketing of aquatic animals include the National
> Marine Fisheries Service of the Department of Commerce, the Fish and
> Wildlife Service of the Department of the Interior, the Food and Drug
> Administration of the Department of Health and Human Services, and the
> Animal and Plant Health Inspection Service of USDA. AMS will consult
> with these agencies in developing its organic standards.
>
> To attend one of the public meetings and provide oral comments,
> individuals should register with AMS before the meeting date by
> calling the National Organic Program at (202) 720-3252 or by
> sending an e-mail message to nop.register@usda.gov. Written comments
> may be sent to Mark Keating, USDA-AMS-TMP-NOP, Room 2510-S, P.O. Box
> 96456, Washington, D.C. 20090-6456. Comments may be submitted by
> e-mail to: aquatic.comment@usda.gov. For more information, call Mark
> Keating at (202) 720-3252.
>
>
>
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Subject: on vacation until may 9
From: wills/nachreiner
Date: Thu, 23 Mar 2000 10:24:29 -0600
unsubscribe
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Subject: nitrite uptake
From: laberge@cil.qc.ca (LABERGE MARC)
Date: Thu, 23 Mar 2000 11:39:01 -0500
Hi all, I have read conflicting reports about plants and nitrite ; can
lettuce absorb nitrites?
Thanks in advance !
Marc Laberge
Mont tremblant
Quebec , Canada
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Subject: Re: Any suggestions
From: "Barry Thomas"
Date: Thu, 23 Mar 2000 20:15:01 -0000
Sam,
Looking back on previous posts to this list, I seem (while aiming to be
brief) to have often managed to either miss out important points or been
abrupt to the point of rudeness. Neither was intended but apologies to
all for both.
> all depends what you need to do--i've found fold up
> floating net cages to be a great solution for all sorts of
> ad-hoc situations--there's a smal group after grading,
> there's some fish you want to keep an eye on, &c.
Yes, indeed. I'm sure nets and cages have many uses but appeared (to me)
unsuitable for this kind of permanent installation (esp as you would
want to alter the relative size of the cages quite frequently).
> on the other hand, i've never seen a movable divider
> that actually kept the fish from moving between the
> groups.
Hmm... well, yes - good point. :)
Just how keen on escaping do you find the fish to be? Will they persist
in trying to get through small gaps?
One possibility I was considering was to fit flexible "flaps" to either
side of the bottom and outside edges of each divider. The flaps would
lie almost parallel to the tank bottom or wall (and might need to be
hinged where they join dividers and sprung to seal them against the
tank - depends on materials used and smoothness of tank).
I'm less happy than I was with the idea anyway - I've been looking again
at numbers re the UVI system and for 4 (fixed) tanks to remain always
above 75% of max capacity, the early growth rate must be substantially
higher than I had thought - removing most of any advantage that might
have been gained by being able to distribute the volume more evenly.
Do you (or anyone) know of any (online) growth curves for tilapia (and
trout)?
For an existing single tank system though, _fixed_ dividers may be a
reasonable upgrade?
Thanks,
Barry
barrythomas@btinternet.com
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| Message 10 |
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Subject: Re: Any suggestions
From: "James Rakocy"
Date: Thu, 23 Mar 2000 17:11:17 -0400
I'm not sure if I've interpreted this comment correctly or not, but let me
explain again. Let's say the plant growing area has been designed to handle
a maximum of 40 lbs. of feed/day. In the four rearing tanks you will have
fish at four stages of growth. At the end of a 6-week period the feeding
rate will approach 40 lbs/day. After you harvest the tank with the
marketable fish (e.g., 500 g), the fish that have been eating the most feed,
and stock it with small fingerlings, say 50 g, the feeding rate to the
system will drop to maybe 30 lbs./day. So you are always working at no less
than 75% of the feeding rate capacity. Now the fish you just stocked will
only be at 10% of the carrying capacity for that tank. Over 24 weeks they
will grow at a steady rate of 2-3 g/day until they reach the carrying
capacity for that tank. Every 6 weeks the system will fluctuate between 75
and 100% of the feeding rate capacity. This is efficient for the system but
not efficient for the individual tank. However, the benefits are that you
do not disturb the fish for 24 weeks and you do not spend money on labor for
stock splitting, method to stay nearer to the maximum capacity. Jim R.
> I'm less happy than I was with the idea anyway - I've been looking again
> at numbers re the UVI system and for 4 (fixed) tanks to remain always
> above 75% of max capacity, the early growth rate must be substantially
> higher than I had thought - removing most of any advantage that might
> have been gained by being able to distribute the volume more evenly.
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| Message 11 |
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Subject: Re: Any suggestions
From: "Barry Thomas"
Date: Fri, 24 Mar 2000 02:37:24 -0000
Jim,
> I'm not sure if I've interpreted this comment correctly or not,
Well, the way it was intended was that I no longer believed that any
space efficiency advantage that a single tank divided into a number of
variable volume segments might have over a comparable multi-tank system,
was worth the the effort.
The reason I no longer believed this was because earlier in this thread
you wrote:
Quote [...
We want the system to always operate near its carrying
capacity with relatively consistent inputs and outputs. Aquaponic
systems are expensive to build and operate. Therefore, you want to
maximize your daily production and work near the top of that sawtooth
graph. You do not want to do batch culture as with ponds. In a pond
fish are stocked at about 10% of the pond's capacity. During their
6-month production cycle they gradually reach the pond's capacity
(100%). With four fish rearing tanks and staggered harvests we never
go below 75% of the system's capacity.
...] End.
Still being an aquaculture newbie I misunderstood this to mean that eg.
a 1000 gal (fish tank volume) system of this type with a max fish
density of 0.5lb/gal would always contain at least 375lb of fish. I was
rather impressed but assumed that I had at first underestimated the rate
of growth when the fish are young.
However, you then wrote:
> but let me explain again. Let's say the plant growing area
> has been designed to handle a maximum of 40 lbs. of feed/day.
> In the four rearing tanks you will have fish at four stages of
> growth. At the end of a 6-week period the feeding rate will
> approach 40 lbs/day. After you harvest the tank with the
> marketable fish (e.g., 500 g), the fish that have been eating
> the most feed, and stock it with small fingerlings, say 50 g,
> the feeding rate to the system will drop to maybe 30 lbs./day.
> So you are always working at no less than 75% of the feeding
> rate capacity. Now the fish you just stocked will only be at 10%
> of the carrying capacity for that tank. Over 24 weeks they
> will grow at a steady rate of 2-3 g/day until they reach the
> carrying capacity for that tank. Every 6 weeks the system will
> fluctuate between 75 and 100% of the feeding rate capacity.
> This is efficient for the system but not efficient for the
> individual tank. However, the benefits are that you do not
> disturb the fish for 24 weeks and you do not spend money on
> labor for stock splitting, method to stay nearer to the maximum
> capacity. Jim R.
Which gives me a different (now hopefully correct) understanding of
"capacity".
It also apparently returns us to square one regarding the pros/cons of
tank division as, although I do see what you mean about the average of
max capacity varying between 75% and 100%, it also (if you see what I
mean) could be said to vary between approx 45% to approx 65% (assuming
perfectly linear growth)?
I realise that there are many factors which influence system design -
just trying to find what the advantages and disadvantages of each
approach are.
Thanks,
Barry
barrythomas@btinternet.com
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