Aquaponics Digest - Mon 12/06/99
Message 1: Re: Seed Supplier
from Adriana Gutierrez & Dennis LaGatta
Message 2: Re: Big customer commitments
from Adriana Gutierrez & Dennis LaGatta
Message 3: Re: Big customer commitments
from "Jay Myers"
Message 4: Re: Big customer commitments
from Jim Sealy Jr
Message 5: Mache
from Adriana Gutierrez & Dennis LaGatta
Message 6: concrete tank construction (formerly greenwater culture in Israel)
from "Mark Brotman"
Message 7: Re: Aloha
from "KevinLReed"
Message 8: Re: Big customer commitments
from S & S Aqua Farm
Message 9: Re: Aloha
from "Wendy Nagurny"
Message 10: Aquaponics archives - a work in progress
from S & S Aqua Farm
Message 11: Copper - was Aloha
from Brian Gracia
Message 12: Re: Aquaponics archives - a work in progress
from atkindw@cwjamaica.com (david w atkinson)
Message 13: Re: concrete tank construction (formerly greenwater culture in Israel)
from "Peter Epperson"
Message 14: slugs and batteries
from "James Lilly"
Message 15: Re: Welcome message and list etiquette
from Virginia Salares
Message 16: Re: slugs and batteries
from "Wendy Nagurny"
Message 17: Humour...Simplest Grant Application
from dreadlox@cwjamaica.com (michael kent barnett)
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| Message 1 |
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Subject: Re: Seed Supplier
From: Adriana Gutierrez & Dennis LaGatta
Date: Mon, 06 Dec 1999 03:19:47 -0500
Hi Dave,
They have an interesting selection but I think they are prohibitively
pricey. If I recall they only sell small packets of seed.
I you look carefully, most of their varieties can be obtained through
other suppliers at a lower cost in bulk quantities including:
Amaranth, Asparagys Bean, Bunching Onion,
> Burdock, Carrot, Celetuce, Chinese Cabbage, Chinese Celery, Chinese
> Kale, Coriander, Garland Chrysanthemum, Green Bean, Hon-Tsai-Tai,
> Kohlrabi, Komatsuma, Lettuce, Luffa, Mint, Mitsuba,
> Oriental Basil,Oriental Cucumber, Oriental Eggplant, Oriental Mustard,
> Oriental Radish,Perilla, Snow Peas, Spinach, Turnip,
Try Johnny's, Stokes, Ornamental Edibles first. It's very difficult to
recoup the cost of very expensive seed, so unless there's a very good
business reason to use really unusual varieties it's best to stay away
from them.
Adriana
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| Message 2 |
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Subject: Re: Big customer commitments
From: Adriana Gutierrez & Dennis LaGatta
Date: Mon, 06 Dec 1999 04:49:22 -0500
What an opportunity Jim, but what a committment. A number of things
come to mind:
1. 80 cases (I assume 3# boxes = 240 #) is a lot of volume. Is his
80-case estimate consistent year-round or is that a peak number? I've
found that customers generally over-estimate their volume requirements.
What % of your business would this represent? Beware of putting all of
your eggs in one basket. Even if you build in a clause to cover your
up-front investment, who wants to work at break-even? I'm curious what
he's paying per pound now, would you mind sharing that info?
If you're going to add significant greenhouse, processing and cooler
space is that the most profitable place to put your money? For example,
if you grew just arugula or a medicinal herb in a 5,000 sq ft greenhouse
could you make more $/sq ft.
2. Check up on this guy - does he have a history of switching/squeezing
suppliers on a regular basis? If so, you could be next. How about
payment terms? One of our biggest, fanciest most prestigious
restaurants in town has a terrible reputation when it comes to payment,
even Sysco has them on COD. Check with wholesalers in the area, not
just the ones he's currently buying from but the ones he isn't buying
from.
3. Packaging - With that kind of volume consider going to 5# boxes; I'm
using 5 pounders with no problems in terms of the leaves getting matted
down and the advantages in packing and handling are considerable.
Instead of 80 cases to set up, pack, seal, store, load and unload you
would have 48. On top of that you have the cost savings from the
boxes. It would be better yet if you could go with a reusuable plastic
but that takes up a lot of holding space at the restaurant and requires
some labor on your part to sterilize.
4. Product - One other thing to evaluate in terms of operations is how
many varieties go in your mix. Cutting down from 12 to 8 makes a huge
difference in the logistics of seeding, planning, etc., etc. and really
doesn't make a huge difference in the end-product. Incorporating just a
few "sweethearts" that don't require regular re-seeding is also very
nice in terms of yield and labor. The varieties I recommend in this
category are Bull's Blood Beets, Bianca Riccia endive and Cerize
lettuce.
Keep us posted Jim. This is very interesting.
Adriana
> I had the buyer for a major white tablecloth restaurant up by the
> airport in Memphis contact me about fresh baby salad greens. Says he can
> use 80 cases each weekend, but wants me to be able to compete with his
> price he's getting on greens shipped next day air from Calif. now.
> Question is what kind of commitment do you think I should push for from
> his end if I gear up for a new customer on this scale, and at reduced
> margins to boot.
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| Message 3 |
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Subject: Re: Big customer commitments
From: "Jay Myers"
Date: Mon, 6 Dec 1999 07:56:13 -0600
Andriana -
Great post - your MBA is showing
Jay
-----Original Message-----
From: Adriana Gutierrez & Dennis LaGatta
To: aquaponics@townsqr.com
Date: Monday, December 06, 1999 3:54 AM
Subject: Re: Big customer commitments
>What an opportunity Jim, but what a committment. A number of things
>come to mind:
>
>1. 80 cases (I assume 3# boxes = 240 #) is a lot of volume. Is his
>80-case estimate consistent year-round or is that a peak number? I've
>found that customers generally over-estimate their volume requirements.
>What % of your business would this represent? Beware of putting all of
>your eggs in one basket. Even if you build in a clause to cover your
>up-front investment, who wants to work at break-even? I'm curious what
>he's paying per pound now, would you mind sharing that info?
>
>If you're going to add significant greenhouse, processing and cooler
>space is that the most profitable place to put your money? For example,
>if you grew just arugula or a medicinal herb in a 5,000 sq ft greenhouse
>could you make more $/sq ft.
>
>2. Check up on this guy - does he have a history of switching/squeezing
>suppliers on a regular basis? If so, you could be next. How about
>payment terms? One of our biggest, fanciest most prestigious
>restaurants in town has a terrible reputation when it comes to payment,
>even Sysco has them on COD. Check with wholesalers in the area, not
>just the ones he's currently buying from but the ones he isn't buying
>from.
>
>3. Packaging - With that kind of volume consider going to 5# boxes; I'm
>using 5 pounders with no problems in terms of the leaves getting matted
>down and the advantages in packing and handling are considerable.
>Instead of 80 cases to set up, pack, seal, store, load and unload you
>would have 48. On top of that you have the cost savings from the
>boxes. It would be better yet if you could go with a reusuable plastic
>but that takes up a lot of holding space at the restaurant and requires
>some labor on your part to sterilize.
>
>4. Product - One other thing to evaluate in terms of operations is how
>many varieties go in your mix. Cutting down from 12 to 8 makes a huge
>difference in the logistics of seeding, planning, etc., etc. and really
>doesn't make a huge difference in the end-product. Incorporating just a
>few "sweethearts" that don't require regular re-seeding is also very
>nice in terms of yield and labor. The varieties I recommend in this
>category are Bull's Blood Beets, Bianca Riccia endive and Cerize
>lettuce.
>
>Keep us posted Jim. This is very interesting.
>
>Adriana
>
>> I had the buyer for a major white tablecloth restaurant up by the
>> airport in Memphis contact me about fresh baby salad greens. Says he can
>> use 80 cases each weekend, but wants me to be able to compete with his
>> price he's getting on greens shipped next day air from Calif. now.
>> Question is what kind of commitment do you think I should push for from
>> his end if I gear up for a new customer on this scale, and at reduced
>> margins to boot.
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| Message 4 |
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Subject: Re: Big customer commitments
From: Jim Sealy Jr
Date: Mon, 06 Dec 1999 07:59:41 -0600
Hi All,
The price issue is a corporate one, not a question of me selling sizzle.
He has the option of using a local supplier as long as they meet the
company's 'buy' price.
We use reusable cases/polybag liners now where practical, and we ship
straight from the greenhouse (no processing).
Guess it would help if I specified what I consider a 'case'. 1 Case =
6-5lb bags/30lb polycrate/bag liner = ~150-240 servings of baby greens
(Arugula, Mache, Mizuna, Red mustard, Spinach, and Tatsio + Lolla Rosa,
green Romaine, and red Romaine)
We run the polycases through a commercial cleaner which resembles a
drive through carwash( Steam cleaning, followed by a UV/ozone bath
sterilisation/drying stage).
Thanks for the input so far. More info later..
Jim
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| Message 5 |
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Subject: Mache
From: Adriana Gutierrez & Dennis LaGatta
Date: Mon, 06 Dec 1999 13:10:47 -0500
Jim,
I see that you have mache in your mix. My customers would love it but
since it takes 50+ days to harvest and is light weight to boot I would
have to price it beyond what anybody wants to pay. How are you growing
your mache?
Adriana
> (Arugula, Mache, Mizuna, Red mustard, Spinach, and Tatsio + Lolla Rosa,
> green Romaine, and red Romaine)
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Subject: concrete tank construction (formerly greenwater culture in Israel)
From: "Mark Brotman"
Date: Mon, 06 Dec 1999 14:07:24 -0500
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Hi Jim,
When I saw your greenwater tanks earlier this year I thought they were just what
folks needed-- it's a really outstanding thing to be able to offer from the
research and extension. Had just a couple of notes on the concrete. While you
are probably already aware of much of the following, I thought I'd also share
with other folks on the list who may have an interest as well. We found that
the concrete tanks outlasted those made with liners, whether the liners were
supported by plywood, galvanized steel or enameled steel, and were far easier to
work with, on and around. When I built the smaller "subsistence" demo tanks on
Saipan, I tried various methods and materials. Included were walls that were
either poured or made of 6" concrete block (a.k.a. "hollow block" or "cinder
block"), and poured floors that used rebar or a standard 6" mesh concrete
reinforcement screen. For your much larger tanks, I would use the rebar, but
let a concrete company determine the appropriate tensile strength of the mix and
the depth of the pour. We typically aimed for a 4" floor on these 4 m round
tanks. On the construction of a series of 8 m tanks, the floors were 6" thick
and reinforced with rebar. (By the way, bumping up tensile strength
significantly really only costs a tiny bit more, at least on Saipan, and the
additional peace of mind may be worth it to you.)
Try to have the whole floor and the footing poured at the same time, rather than
in small batches, to ensure slab integrity.
With the hollow block, the walls were laid up after the floor was poured, which
made it easy to provide structural continuity between wall, floor and footing.
Rebar was tied in between the layers of block to provide additional strength
during our occasional earthquakes.
The tanks with poured walls had their floors poured after the walls had started
to cure, but the frame work for the floor support (wire mesh or rebar) was
already in place. The poured walls were also reinforced with a rebar frame to
help withstand the intermittant shaking.
The joint between the wall and the floor/footing was made to look what you'd see
in a bathtub, and was done by filling in with morter mix. This invariably made
the seal tight and of course flow dynamics were improved too.
A final note, the same mortar mix was made into a water proofing agent by adding
"Sahara," which is made in the Philippines and looks like (and may very well be)
powdered Elmer's glue. It's just the cheapest stuff I could find ($2 a bag, one
bag per 50 lb sack or mortar mix) that could be used for waterproofing potable
water tanks.
I learned quite a bit by talking to the concrete contractors on the island and
it soon became apparent who knew the business best. Perhaps letting your
concrete companies there put in bids for the work would help find the best
answers for this particular situation?
Mark
--
Mark J. Brotman
Aquaculturist
CropKing
5050 Greenwich Rd.
Seville, OH 44273
Tel: 330/769-2002, Fax: 330/769-2616
Email: mbrotman@cropking.com
James Rakocy wrote:
> Sam, We are working on greenwater technology here in the Virgin Islands. We
> plan to build two circular greenwater tanks early next year. They will be
> 200 m2. In our experiments so far we have been able to produce 17 kg/m3
> using Nile tilapia. Our water exchange rate is much lower, less than 1%.
> We only remove water containing sludge, which is a nice dark green color,
> indicating the removal of dead algal cells. I would be interested to learn
> about construction techniques. We plan to build one tank with a standard
> block wall and the tank will be lined with 30 mil high density polyethylene.
> We will slope the bottom to a center drain by 1 to 2% and insert a 1 m3 cone
> (45 degree slope made of thicker lining material) in the center of the tank.
> The other method will use a speed block wall and a concrete bottom. I
> understand that speed blocks involves a combination of poured concrete core
> and a block outer wall, almost like a permanent form. I want to compare the
> cost, ease of construction and durability of these methods. I'm not too
> familiar with concrete work. I would like to know the best way to pour a
> 200 m2 concrete floor. How thick should it be? What type of reinforcing is
> best? There will be a 18 inch wide by 1 foot deep footing around the
> perimeter. How does one assure a good seal between the wall and the footing
> and the floor and the footing? Also, how does one make a 45 degree cone out
> of concrete? Does it require a form or can you use a drier mix and shape it
> without a form. I understand that many Israeli greenwater systems are out
> of use? Is this true and why? Anyone good with concrete? Jim R.
>
> ----- Original Message -----
> From: Sam Levy
> To:
> Sent: Friday, December 03, 1999 1:39 AM
> Subject: Re: Fw: Greenwater Culture in Israel.
>
> > ted--
> >
> > hope you get this before you're off list.
> >
> > greenwater is typically done here in earthen ponds or in lined ponds using
> > water from earthen ponds.
> >
> > what i will describe here is a system that's a little different but deals
> > with some of the issues you raise.
> >
> > this strategy is practiced in plastic lined (or concrete) ponds and is
> > designed to maximize the utilization of nutrients.
> >
> > the aerators (paddlewheel / fountain) are placed to maximize the continued
> > presence of particulate matter in the water column. the tilapia are fed a
> > commercial diet of 25 - 35% protein (depending upon availability) and 3 -
> 5%
> > lipid. water exchange is 5 - 15% daily (sometimes as low as 3%). the
> ponds
> > are typically flushed twice/day to eliminate settled solids. the fish are
> > stocked for growout at around 100 grams. planned maximum density for a
> pond
> > will be 16 - 20 kg/sq m. this strategy is practiced in ponds of 100 - 250
> > sq m (possibly up to 400 sq m). small juveniles will be reared to around
> 5
> > - 7 kg/m @ 5 grams. advanced juveniles to 10-15 kg/m.
> >
> > the essential process is the the conversion of carbon and nitrogen into
> > bacterial protein (floc) which the fish ingest. again, this is a strategy
> > for maximizing feed utilization and may result in slower growth and lower
> > densities compared to other management systems.
> >
> > it is also a system that requires careful monitoring for oxygen and
> > nitrogenous wastes--as you can well imagine. the water will often be a
> > lovely brown color.
> >
> > tilapia do well and carp may be added to help keep the bottom stirred
> up--it
> > remains to be tested with other species.
> >
> > looking forward to your return,
> >
> > sam
> >
> > >From: "TGTX"
> > >Subject: Fw: Greenwater Culture in Israel.
> >
> > >
> > > > I would very much like to hear from any Israeli Tilapia farmers on the
> > > > fundamentals of greenwater Tilapia culture as it is practiced in
> Israel.
> > > >
> > > > 1) How protein content (%) in feed pellets may be lowered in
> greenwater
> > > > culture, and in what manner (in stages or degrees, or at all growth
> > >stages)
> > > > to take advantage of the algae & suspended bacteria food source and
> the
> > > > algae-heterotrophic bacteria function of assimilating nitrogenous
> waste
> > >into
> > > > their biomass.
> > > >
> > >
> > > > 4) I dimly recall some carbon isotope studies of greenwater Tilapia
> > >culture
> > > > conducted (I believe) in Israel, indicating that approximately half of
> > >the
> > > > assimilated carbon that went into the fish came from the artificial
> > >pellet,
> > > > whereas the other half orginated from photosynthate carbon and
> possibly
> > > > recycled ambient carbon sources from heterotrophic bacterial
> > >biomass...can
> >
> > > > Sincerely,
> > > >
> > > > Ted Ground
> > >
> > >
> >
> > ______________________________________________________
> > Get Your Private, Free Email at http://www.hotmail.com
> >
On the web at http://www.cropking.com
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Subject: Re: Aloha
From: "KevinLReed"
Date: Mon, 6 Dec 1999 10:08:03 -1000
Aloha,
Good ideas about the copper as these guys don't all seem to like the beer in
the traps ... maybe I should try imported ...
I will try to find some copper foil but I may have no luck finding it on
this little island ... any by mail you know of?
I am going to try some 1/2 copper tubing we have handy for a test.
The snails are about two inches long but it may get them all the way off of
the ground as they climb over. Will let you know how it works
Aloha
Kevin
----- Original Message -----
From: "Wendy Nagurny"
To: "Aquaponics"
Sent: Sunday, December 05, 1999 7:03 PM
Subject: Re: Aloha
> I hear copper is
> >lethal to them too, so installing barriers around your beds should take
> >care of them unless they fly.
>
> I am not an expert on slug/snail anatomy, but the copper deterrent thing
was
> explained to me like this: When the slug's slime comes in contact with
> copper, a chemical in the slim interacts with the copper and forms a low
> voltage battery. There are two sense organs of some kind on the slug's
> underside; one near the head end and the other near the tail end. When
the
> slime/copper battery is connected between these two sense organs, it
annoys
> the bejeebers out of the slug so it avoids the copper barrier. The
copper
> barrier must be wide enough so that nearly the slugs whole body must be on
> it for the copper barrier to work. A slug will just crawl over a thin
wire.
> Copper foil nailed to a wide surface of a 1X2 is usually sufficient unless
> you have some real big 'uns.
>
> I have some slug problems in my hostas. I have thought about covering
some
> 1X2's with copper foil and tooling some pretty patterns in it for use as
bed
> edging.
>
>
> >
> >>
> >
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| Message 8 |
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Subject: Re: Big customer commitments
From: S & S Aqua Farm
Date: Mon, 06 Dec 1999 17:58:36 -0600
At 08:53 PM 12/05/1999 -0600, Jim wrote:
>I had the buyer for a major white tablecloth restaurant up by the
>airport in Memphis contact me about fresh baby salad greens. Says he can
>use 80 cases each weekend, but wants me to be able to compete with his
>price he's getting on greens shipped next day air from Calif. now.
>Question is what kind of commitment do you think I should push for from
>his end if I gear up for a new customer on this scale, and at reduced
>margins to boot.
>Jim Sealy Jr.
Jim - I don't think you've said what type of additions or adjustments to
your current systems you'd have to make in order to supply this market in
addition to your others. Would you back off any of your other markets
(developed or developing) in order to take care of this account? Or would
you plan a big expansion?
Developing this kind of "local" market is what most of us hope for, I think;
and the opportunity to get into it solidly can sometimes cause us not to
view things realistically (not that you fall in this category, just
"thinkin'" out loud).
I saw lots of good information in the responses you've received so far. The
one that stands out from our experiences was Adriana's advice:
>
>2. Check up on this guy - does he have a history of switching/squeezing
>suppliers on a regular basis? If so, you could be next. How about
>payment terms? One of our biggest, fanciest most prestigious
>restaurants in town has a terrible reputation when it comes to payment,
>even Sysco has them on COD. Check with wholesalers in the area, not
>just the ones he's currently buying from but the ones he isn't buying
>from.
Questions to ask:
Does the restaurant buy all their product through one broker? Are they the
most powerful in town? Can they put pressure on the restaurant to buy only
product they supply by withholding other needed products? We've found the
food business to be highly political, and these are things you need to be
aware of up front; although with your current markets you probably have a
better handle on things than we did going in.
I believe that it's very difficult to hold buyers, at least the broker we've
dealt with and one other we had second-hand information on, to a commitment
unless you have some legal assistance in drawing up your contract. Even
then, should they default, at what expense and how long would it take to
collect or receive compensation? And what condition would your production
facility be in without that "guaranteed" income on a timely basis.
What it comes down to is probably decided better face-to-face with the
buyer. If you meet at his location, you'll have an idea of his value to the
restaurant, his longevity, how much weight his decisions carry; and have the
opportunity, possibly, to speak to the head chef who no doubt will have a
lot to do with the decisions. I think a personal visit is in order before
you get into final negotiations and building plans.
As for the form of the commitment - always in writing, and probably best
with a lawyer's help if you're talking about a major expansion. My 2
cents...:>)
Paula
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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| Message 9 |
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Subject: Re: Aloha
From: "Wendy Nagurny"
Date: Mon, 6 Dec 1999 19:27:59 -0500
>Aloha,
>Good ideas about the copper as these guys don't all seem to like the beer
in
>the traps ... maybe I should try imported ...
>I will try to find some copper foil but I may have no luck finding it on
>this little island ... any by mail you know of?
If you want to try copper foil, you may have to seek out ham radio or other
RF suppliers. The ground plain foil used for RF applications is usually
available. If no luck on the island with this, try
http://www.metal-cable.com/
They sell in non-industrial quantities. I don't know if they are the
cheapest for what you want, but their prices aren't bad. You may contact
them, and ask if they have any damaged rolls. Foil that has gotten dinged
up may be unsuitable for RF applications, but fine for slug control, so you
may be able to get some discounted.
Wendy
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| Message 10 |
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Subject: Aquaponics archives - a work in progress
From: S & S Aqua Farm
Date: Mon, 06 Dec 1999 19:23:45 -0600
In Jim Sealy's spare time (I guess we can all see that he really doesn't
have any), he's building our archive file at:
http://www.i55mall.com/aquaponics/
He says, as his status report today, "but have all the heavy lifting done
now so the rest should move more easily."
So far as I've had time to check, all the digest versions from December 4,
1999 back through September 1999 are now up for any of you wanting to just
review previous days discussions. All the digests back through December
1997 will be put up, then Jim promises to add in search capabilities.
Thanks, Jim, for this good effort. It will certainly be appreciated.
Paula
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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| Message 11 |
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Subject: Copper - was Aloha
From: Brian Gracia
Date: Mon, 06 Dec 1999 19:47:54 -0600
At 06:27 PM 12/6/99 , you wrote:
>
>
>>Aloha,
>>Good ideas about the copper as these guys don't all seem to like the beer
>in
>>the traps ... maybe I should try imported ...
>>I will try to find some copper foil but I may have no luck finding it on
>>this little island ... any by mail you know of?
>
Got a good building supply store or hardware store? Try calling around for
copper flashing! It is paper backed and comes in a roll.
Brian Gracia
********************************************
Better Produce through Better Control
********************************************
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| Message 12 |
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Subject: Re: Aquaponics archives - a work in progress
From: atkindw@cwjamaica.com (david w atkinson)
Date: Mon, 06 Dec 1999 20:40:01 -0800
Way to go Jim.
David A
At 07:23 PM 12/06/1999 -0600, you wrote:
>In Jim Sealy's spare time (I guess we can all see that he really doesn't
>have any), he's building our archive file at:
>
>http://www.i55mall.com/aquaponics/
>
>He says, as his status report today, "but have all the heavy lifting done
>now so the rest should move more easily."
>
>So far as I've had time to check, all the digest versions from December 4,
>1999 back through September 1999 are now up for any of you wanting to just
>review previous days discussions. All the digests back through December
>1997 will be put up, then Jim promises to add in search capabilities.
>
>Thanks, Jim, for this good effort. It will certainly be appreciated.
>
>Paula
>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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| Message 13 |
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Re: concrete tank construction (formerly greenwater culture in Israel)
From: "Peter Epperson"
Date: Mon, 6 Dec 1999 16:28:33 -1000
You folks might try ferrocement construction for your holding tanks. I have
built many concrete fish ponds and tanks using this method. It is not
difficult, uses less materials than conventional concrete and is
exceptionally strong and durable. Incidentally, I repair cinder block tanks
frequently. People here in Hawaii have built them for water storage and
found out after a few years that they are difficult to make watertight and
don't last. Check out my website www.ferrotanks.com and follow the links to
tanks and the cutaway drawing. Peter
>Hi Jim,
>
>When I saw your greenwater tanks earlier this year I thought they were just
what
>folks needed-- it's a really outstanding thing to be able to offer from the
>research and extension. Had just a couple of notes on the concrete. While
you
>are probably already aware of much of the following, I thought I'd also
share
>with other folks on the list who may have an interest as well. We found
that
>the concrete tanks outlasted those made with liners, whether the liners
were
>supported by plywood, galvanized steel or enameled steel, and were far
easier to
>work with, on and around. When I built the smaller "subsistence" demo
tanks on
>Saipan, I tried various methods and materials. Included were walls that
were
>either poured or made of 6" concrete block (a.k.a. "hollow block" or
"cinder
>block"), and poured floors that used rebar or a standard 6" mesh concrete
>reinforcement screen. For your much larger tanks, I would use the rebar,
but
>let a concrete company determine the appropriate tensile strength of the
mix and
>the depth of the pour. We typically aimed for a 4" floor on these 4 m
round
>tanks. On the construction of a series of 8 m tanks, the floors were 6"
thick
>and reinforced with rebar. (By the way, bumping up tensile strength
>significantly really only costs a tiny bit more, at least on Saipan, and
the
>additional peace of mind may be worth it to you.)
>
>Try to have the whole floor and the footing poured at the same time, rather
than
>in small batches, to ensure slab integrity.
>
>With the hollow block, the walls were laid up after the floor was poured,
which
>made it easy to provide structural continuity between wall, floor and
footing.
>Rebar was tied in between the layers of block to provide additional
strength
>during our occasional earthquakes.
>
>The tanks with poured walls had their floors poured after the walls had
started
>to cure, but the frame work for the floor support (wire mesh or rebar) was
>already in place. The poured walls were also reinforced with a rebar frame
to
>help withstand the intermittant shaking.
>
>The joint between the wall and the floor/footing was made to look what
you'd see
>in a bathtub, and was done by filling in with morter mix. This invariably
made
>the seal tight and of course flow dynamics were improved too.
>
>A final note, the same mortar mix was made into a water proofing agent by
adding
>"Sahara," which is made in the Philippines and looks like (and may very
well be)
>powdered Elmer's glue. It's just the cheapest stuff I could find ($2 a
bag, one
>bag per 50 lb sack or mortar mix) that could be used for waterproofing
potable
>water tanks.
>
>I learned quite a bit by talking to the concrete contractors on the island
and
>it soon became apparent who knew the business best. Perhaps letting your
>concrete companies there put in bids for the work would help find the best
>answers for this particular situation?
>
>Mark
>
>--
>Mark J. Brotman
>Aquaculturist
>CropKing
>5050 Greenwich Rd.
>Seville, OH 44273
>Tel: 330/769-2002, Fax: 330/769-2616
>Email: mbrotman@cropking.com
>
>
>
>
>James Rakocy wrote:
>
>> Sam, We are working on greenwater technology here in the Virgin Islands.
We
>> plan to build two circular greenwater tanks early next year. They will
be
>> 200 m2. In our experiments so far we have been able to produce 17 kg/m3
>> using Nile tilapia. Our water exchange rate is much lower, less than 1%.
>> We only remove water containing sludge, which is a nice dark green color,
>> indicating the removal of dead algal cells. I would be interested to
learn
>> about construction techniques. We plan to build one tank with a standard
>> block wall and the tank will be lined with 30 mil high density
polyethylene.
>> We will slope the bottom to a center drain by 1 to 2% and insert a 1 m3
cone
>> (45 degree slope made of thicker lining material) in the center of the
tank.
>> The other method will use a speed block wall and a concrete bottom. I
>> understand that speed blocks involves a combination of poured concrete
core
>> and a block outer wall, almost like a permanent form. I want to compare
the
>> cost, ease of construction and durability of these methods. I'm not too
>> familiar with concrete work. I would like to know the best way to pour a
>> 200 m2 concrete floor. How thick should it be? What type of reinforcing
is
>> best? There will be a 18 inch wide by 1 foot deep footing around the
>> perimeter. How does one assure a good seal between the wall and the
footing
>> and the floor and the footing? Also, how does one make a 45 degree cone
out
>> of concrete? Does it require a form or can you use a drier mix and shape
it
>> without a form. I understand that many Israeli greenwater systems are
out
>> of use? Is this true and why? Anyone good with concrete? Jim R.
>>
>> ----- Original Message -----
>> From: Sam Levy
>> To:
>> Sent: Friday, December 03, 1999 1:39 AM
>> Subject: Re: Fw: Greenwater Culture in Israel.
>>
>> > ted--
>> >
>> > hope you get this before you're off list.
>> >
>> > greenwater is typically done here in earthen ponds or in lined ponds
using
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