Aquaponics Digest - Sat 03/11/00
Message 1: (no subject)
from Jennifer Maynard
Message 2: Re: Aquaponics Digest - Fri 03/10/00
from DAVEINBHAM
Message 3: Re: Any suggestions
from MUDDTOO
Message 4: Re: Any suggestions
from "Barry Thomas"
Message 5: Re: System and greenhouse for sale
from "bennett"
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Subject: (no subject)
From: Jennifer Maynard
Date: Sat, 11 Mar 2000 03:55:41 -0400
unsubscribe
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Subject: Re: Aquaponics Digest - Fri 03/10/00
From: DAVEINBHAM
Date: Sat, 11 Mar 2000 10:41:05 EST
In a message dated 03/11/2000 12:04:46 AM Central Standard Time,
aquaponics-digest-request@townsqr.com writes:
<< You should take our 7-day course at the end of June if
you want to learn more about aquaponic systems. Jim R.
>>
******************************************************************************
Jim,
Please tell us more about your 7-day course.
Regards,
Dave
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Subject: Re: Any suggestions
From: MUDDTOO
Date: Sat, 11 Mar 2000 11:59:56 EST
In a message dated 3/10/00 7:26:03 AM Pacific Standard Time, jrakocy@uvi.edu
writes:
> By steady state I mean nutrient levels will fluctuate within an
> acceptable range. You should take our 7-day course at the end of June if
> you want to learn more about aquaponic systems. Jim R.
>
So, if I understand this right, by selecting the correct volumn of plantsone
can control the nutrient level. It sounds like it may be a delicate balance
between strong enough for the plants yet clean enough for the fish. How do
you determine the cutoff, the point where the water in the system is just
right for the fish? What would that number be in EC?
In hydroponics I set the EC for lettuce at around 1500 uS and for tomatoes at
about 2500 to 3000 uS. It would seem the level set for lettuce (1500uS)
would be a lot easier on the fish then the other.
One last thought, would one control the relative strength of the nutrient in
the water,in a mature system, by controlling the amount of feed fed?
Thanks for the help, Joel
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Subject: Re: Any suggestions
From: "Barry Thomas"
Date: Sat, 11 Mar 2000 20:03:55 -0000
Joel,
The "growing area" thread from a while back has some more detailed info
from Jim Rakocy on this. I found the UVI and ATTRA sites also very
useful. I believe the following to be true but it may not be. Just
thought it might be useful as another perspective or at least provide
some discussion material as it gets ripped to bits. :)
> One last thought, would one control the relative strength
> of the nutrient in the water,in a mature system, by controlling
> the amount of feed fed?
I think, to an extent perhaps but the amount fed is determined mainly by
the fish density which, if only a percentage is harvested at a time,
should remain fairly constant. Doing the same with the plants results in
a constant rate of conversion there as well.
I've abused 'constant' twice here. These values only really approach
constant when averaged over time. Assuming a UVI type system with four
tanks and a six week fish harvest of 25% then a graph of the rate of
fish waste production over, say, a year would show as a sawtooth - slow
climb to a peak followed by a short, sharp fall every 6 weeks. 25% of
the lettuce is harvested a week giving another, higher frequency
sawtooth for the rate of uptake/conversion. Subtract this from the first
and you get a wave that averages around zero (if ratio of plant area to
fish mass is correct) but is rougher still. Increasing the harvest
frequency further, reduces the range of the values, bringing the overall
nutrient level closer to a constant. This raft system goes so far along
this route and then smooths things out by having a small plant area to
system water volume (rough analog to using water as passive heat storage
in GHs - maybe not so rough now I think about it, imagine if a day
lasted 24 weeks...).
So from what I can gather, an actual graph of nutrient levels over time
in such a system would display as a very low amplitude sawtooth caused
mainly by a slight (intentional) accumulation of nutrients, punctuated
by regular dumping of small amounts of water from the system when solids
are removed. This should also prevent any build-up of individual
components of the nutrient (the water added to replace that transpired
or evaporated won't be helping much in this).
Like I say, just my current understanding...
Barry
barrythomas@btinternet.com
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Subject: Re: System and greenhouse for sale
From: "bennett"
Date: Sat, 11 Mar 2000 21:21:33 -0500
Would you consider selling the system separate from the greenhouse? If so,
how much would you want for it?
-----Original Message-----
From: Robin Jenkins
To: aquaponics@townsq.co
Date: Friday, March 10, 2000 8:48 PM
Subject: System and greenhouse for sale
>Hi everyone,
>
>My name is Robin Jenkins and I've been on this list for a little over a
year
>now. You are really a great bunch of people and the list is one of the
>friendliest and most cooperative I've encountered on the net. I asked
>permission from Paula to make this offer in light of the non-disclosure
>agreement we have and she graciously consented.
>
>I started my system last February for several reasons: an interest in
>integrated gray water treatment in residential dwellings, an interest in a
>small business venture in biointensive agriculture, and I like fish and
>plants so it seemed like a natural. Time constraints and new interests
make
>it so that I can't give aquaponics the kind of attention it demands for the
>foreseeable future, so I must shut it down. I hate to just junk all the
>components but that is what will eventually happen whether I want to or
not.
>I know that there are those on this list who could make use of parts of if
>not the whole system.
>
>How much? It's negotiable. Let me say that I really don't care to make
any
>money, just recoup a portion of the investment in terms of the materials
>used. The system has worked beautifully for me since I cranked it up. The
>design principles follow closely the S & S model, with a few changes. I
>have spent well over $6500 on the whole thing and have receipts to prove
it.
>So would $4750 be fair? Make me an offer. I will come and help you set it
>up and get it going for the price of the hotel stay, maybe less if you
live
>somewhere I would want to vacation. I'll show you how to program the
>computer and throw in a nursery tank I made out of a 55 gallon plastic
>drum! Now that's a deal! The whole system and greenhouse can be loaded in
>a pickup and 16' flatbed trailer.
>
>System:
>
>Fish tank is a 1000 gallon sloped-bottom, blue poly tank. I currently
have
>300 Pennyfish tilapia of staggered ages stocked. The tank is supported on
a
>wooden stand that keeps most of the water above the level of the grow beds.
>A 3" PVC "manifold" pipe drains the tank. A 3" PVC 24volt motorized drain
>valve is controlled by a Programmable Logic Controller (PLC), a small
>industrial computer. It opens every two hours and closes when the grow
beds
>fill up with water. 1" PVC pipe taps off of the manifold for each of the 5
>grow beds, with a 1" PVC ball valve to cut of each individual bed and
>regulate water flow. 1" PVC irrigation grids help to start plants, then
are
>removed for the flood and drain phase. There is another 24volt motorized
>drain valve on the drain for all of the beds. It controls the flood and
>drain cycle and also works off of the PLC. Water drains by gravity into
the
>grow beds and then into another 800 gallon reservoir tank that is below the
>level of the grow beds. This reservoir contains the only pump that is
>controlled by a level control in the main fish tank. Everything is fail
>safe, so if a motor valve fails, or a pump fails, or the computer fails,
>the fish tank is not emptied. I also have a spare for everything, motor
>valves, pumps, etc.
>
>The PLC is easy to program and has several more inputs and outputs
available
>for things such as automatic feeders, alarms, monitors, etc. It is also
>expandable. The pump is 1/4 hp and only runs 15% of the time if you keep a
>2 hour flood and drain cycle. My cycle is: water circulates over the grow
>beds for 7 minutes. This gets the water in the fish tank spinning like a
>toilet. After 7 minutes, the drain closes and the beds fill up. They
stay
>flooded for 30 minutes and then drain. Two hours pass before the cycle
>begins again.
>
>Grow beds are 3/4" Marine grade plywood coated on the inside with a food
>grade epoxy. There are 4- 48" x 72", and 1-48" x 84". Each has 2x4 base
>and cynderblock stands. They are lined now with 6 mil poly-plastic, but I
>would go back with 20 mil EPDM pond liner or better.
>
>If you could work it you could also have my gravel and lava rock grow
media,
>complete with one of my favorite parts of the system- Eisenia Foetida!
Red
>Wriggler worms! I have an excellent population and they keep things clean!
>
>
>Greenhouse:
>
>The greenhouse is wood framed, 14' x 20' lean-to. 12' at the highest down
>to 7' at the front. It is plenty roomy, and big enough to keep from
>overheating. It has 1 wind turbine as a vent, but I recommend installing
2
>more, they're cheap. The glazing is corrugated Polycarbonate, lifetime
>guaranteed. Glazed inside and out on the roof and front. The roof and
>front are glazed with the Poly Carb. and the sides are done with cheap 6
mil
>poly plastic. Wood strips screw on the poly and the whole outside can be
>replaced in an afternoon by one person. The roof is 2x6 joists on 48"
>centers, and the walls are 2x4 studs on 24" centers. There is a good
storm
>screen door that came from my mother's house. The whole thing is screwed
>together and can be disassembled and moved.
>
>I think if you live in the southern latitudes, you could go without the
>glazing on the inside and use it to glaze the sides. I heated the water
>with a homemade heater using water heater elements and styrofoam and the
>warm water kept the greenhouse toasty all winter long here in Lubbock, TX.
>
>Whether or not you're interested in buying, all of you are welcome to
come
>and take a look at my system any time. It is still up and running with
>tomatoes, peppers, basil, aloe vera, swiss chard, and most amazing -
>Ficus Trees! You can also contact me off list if you want at
>hotrob@swbell.net . Thanks for reading and all the information you've
>provided over the last few months. I especially enjoy you Ted (TGTX).
Like
>to meet you some day. Stop in if you're in my neck of the woods, 'course
>there are no woods here, just wind and dust.
>
>Robin Jenkins and /. .\
> (.)
>
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>
>
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