Aquaponics Digest - Thu 02/04/99
Message 1: Re: Fresh Water Crays in Aquaponics
from "Jorg D. Ostrowski"
Message 2: Re: starting out
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 3: Re: Gravel beds (was Tomato Varieties)
from james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Message 4: Re: starting out
from "Glennert Riedel"
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| Message 1 |
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Subject: Re: Fresh Water Crays in Aquaponics
From: "Jorg D. Ostrowski"
Date: Thu, 4 Feb 1999 07:20:03 -0700 (MST)
Michael: I have 5 fresh water crayfish in my GreyWater GardenWall which
includes gravel filters, waterfalls, hydroponics, marshes and fish tanks
in a 40 CF corner of our integrated passive solar greenhouse for treating
greywater and raising food. I do NOT feed my crayfish anything. They seem
to survive on plant material so far. But what do they prefer to eat? They
can also take the strongest dose of greywater, whereas the minnows cannot.
But what function do these crayfish offer my system? Would they help to
filter the water? Perhaps to clean up the bottom, or turn-over the gravel?
*****************************************************************************
Jorg-Dietram Ostrowski, M. Arch. A.S. (MIT), B. Arch. (Toronto), Ecotect
- in full-time professional practice since 1976 (Straw Bale since 1978),
environmental/architectural design, ecological planning, consulting
on sustainable buildings/communities. Lectures, seminars, workshops.
- 3 residential demonstration projects in Canada, +80,000 visitors
- college campus and office tower recofit under construction
- living a conserver lifestyle & working in a sustainable home and office
ACE, ARE, ACT, ASH-Incs., Phone: (403) 239-1882, Fax: (403) 547-2671
Web Site [under construction]: http://www.ucalgary.ca/~jdo/ecotecture.htm
e-mail:
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Subject: Re: starting out
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Thu, 4 Feb 1999 17:31:11 -0400 (AST)
We have good stocks of red and Nile tilapia at the University of the Virgin
Islands Agricultural Experiment Station (St. Croix). We sent some of these
stocks to Trinidad. They are being used by Caroni, a goverment agricultural
enterprise. This is probably your closest source. We've never added bacteria
to our growing beds, but Bioshelters, the largest aquaponic operation in the
U.S., does, and this would probably be a fertile area for
discussion/research. We are also offering an aquaponics training program in
June or July. Jim R.
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Subject: Re: Gravel beds (was Tomato Varieties)
From: james.rakocy@uvi.edu (James Rakocy, Ph.D.)
Date: Thu, 4 Feb 1999 18:31:56 -0400 (AST)
Gordon, What we did is use 3-inch PVC pipe, Schedule 40. We placed these
lengthwise (18.5 ft long) down the tank bottom one foot apart and 6 inches
off the side. Before we did this we took a router and put a notch every foot
along the top of the pipe. We then cut 3/4 inch rebar in 4-ft lengths (our
tanks were 4 ft. wide, 20 ft. long). We placed the rebar in the pipes at
1-ft. intervals so the whole assemblage held together tightly and the PVC
and rebar were flush with the surface. On top of that we laid 1/2 inch vinyl
coated galvanized hardware cloth. At the ends we turned up the hardware
cloth so it was vertical and stapled it to a 2x4-inch wood frame. This gave
us a 9-inch sump at each end. We put 8 inches of gravel over the hardware
cloth. There was no sag in the hardware cloth as the sections between
supports were 1 square ft. We placed some male tilapia fingerlings under the
gravel to prevent any solid matter from accumulating. This was a
reciprocating system that alternately flooded and drained using a U-tube
siphon. As to your second question. I'm sure you could scale up this gravel
tank a bit, but I personally shoveled and graded the gravel for twelve of
these tanks and I would never want to do that again. And what if you had to
clean or change the gravel because it became choked with roots? Maybe you
could clean a 20 x 4 ft. tank, but could you imagine making and cleaning a
tank 30 ft. wide by 400 ft long (0.275 acres), a size that is not altogether
unrealistic for a large commercial operation consisting of many production
units that would be competitive with today's field operations. It would be
very easy to construct a raft system this large. Just build a 16 inch
perimeter wall an install a liner. Polystyrene sheets that are 4 x 8 ft. are
light and easily removed. Most roots are removed with the sheets during
harvest. What remains can easily be hosed down to a drain if necessary. This
may be an extreme example, but I want to illustrate the point that gravel
systems have size limitations. Jim R.
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Subject: Re: starting out
From: "Glennert Riedel"
Date: Thu, 04 Feb 1999 18:56:26 PST
>
Thanks Jim, what will it cost me to get some Tilapia? I'm also conserned
about the time it will take to get to Curacao. Will the fish survive the
trip?
How many fish do you recomend me to start with and witch type, Red or
Nile?
Glennert
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