Aquaponics Digest - Fri 05/12/00
Message 1: Re : Attie
from laberge@cil.qc.ca (LABERGE MARC)
Message 2: Re: pH control
from "Wendy Nagurny"
Message 3: Re: PVC glazing
from "Loren"
Message 4: Re: PVC glazing
from William Evans
Message 5: Re: PVC glazing
from Sojourner
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| Message 1 |
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Subject: Re : Attie
From: laberge@cil.qc.ca (LABERGE MARC)
Date: Fri, 12 May 2000 16:42:08 -0400
Attie I prefer talking threw the group in order to share information and on
a good day get feed back from the group.
<>
Hi Attie it's been a while...
I have never worked with tilapia but can say for sure they are a much
hardier fish than trout. I changed my system 4 times and now have a
combination trickling gravel biofilter along with floating rafts. The reason
for the rafts is that in commercial lettuce growing up in cold climates ,
greenhouse heating costs a fortune , in order to make a profit greenhouse
space must be used to the maximum. I originally read that the roots alone
could provide enough biofiltration to turn ammonia into nitrate. Not so , or
least not so at 15C , using 57 grams of feed per M2 of growing space. I had
to incorporate a trickling biofilter using the S&S ratio of 1 volume fish
water for 2 volumes gravel. I no longer remove any fish waste from the
water; everything is returned , sprayed over the gravel. I have had a small
nitrite problem since the beginning and now believe it is caused by partial
denitrification in my biofilter due to anaerobic conditions and low
alkalinity. I have been trying like mad to maintain alkalinity over 50ppm
while keeping my pH at ~7.0 but am not successful. This nitrite is
preventing me from loading my system with the proper amount of fish , which
in turn is preventing me from feeding the amount I am supposed to put in the
system. This is turn is causing a lack of nutrients to my lettuce which are
pale green-yellow. I can fix this problem by adding cheated elements but do
not want to; this would defy the whole purpose of the project , which is to
add the absolute minimum to the system. After visiting the worlds largest
hydroponic lettuce producers in Mirabel Quebec , I decided to switch to
Boston lettuce and compare results with them.
In certain systems where fish waste is not removed , apparently you do not
have to adjust pH or anything... everything falls into equilibrium... I have
yet to succeed at 15C and doubling my biofilter size is out of the question
because this would not be feasible commercially, well at least not up here
in Quebec.
Marc Laberge
Mont Tremblant
Quebec , Canada
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Subject: Re: pH control
From: "Wendy Nagurny"
Date: Fri, 12 May 2000 16:50:57 -0400
Hi Steve,
My first question is why do you want to lower your pH? Do you wish to add
some species the requires a lower pH? Shifting the pH in a natural body of
water is a never ending struggle as it will always want to go back to its
natural balance. The pH of water (whether it is in a pond or in a tank) is
an effect of other parameters such as the water hardness and metabolism of
the species already within the system. Just adding something to "adjust the
pH" without addressing these other parameters will just cause frustration
and a bunch of dead species. Usually for a pH that high, the water will
also be quite hard which acts as buffering. You will need to add a lot of
something acid to cause any permanent (temporary shifts will be seen, but
the pH will rebound). This can be likened to treating the fever associated
with a bad infection with aspirin without addressing the infection. The
body
temp will lower, but jump back up when the aspirin wears off. You must deal
with the infection if you want the body temp to stay down. First, the water
must be softened by removing the the mineral content of the water. In a
tank this is as easy as making partial water changes with distilled water.
Here, the pH may just shift down itself. Not an easy feat in a pond which
may have access to virtually unlimited minerals. What I'm trying to get at
is, you must really NEED to lower your pH to even bother. Why do you want
to lower your pH?
Wendy
>Hi Gang,
>
>I need to ask a question that is "somewhat" unrelated to aquaponics or
>hydroponics.
>
>I have a pond that is apprx. 1/4 - 1/3 acre and probably averages 5' in
>depth. (I have a shallow end that is inches and a deep center that is
apprx.
>12'.) I was not fortunate enough to hit a spring when I had the pond dug.
>Therefore, all water is from ground water.
>
>I read a chart that shows un-ionized ammonia is directly related to temp.
>and pH. Well, there is nothing I can do about the temp. The pH of the pond
>was 9.5 +/-. I am trying to get the pH down to apprx. 7.0. I have been
>adding muriatic acid. I have added 10 gal so far and the pH is down to 8.5.
>
>I am adding the acid a gallon at a time at a cost of $2.37/gal. Anyone have
>any suggestions as to a better way to do this?
>
>Thanks.......Steve
>
>
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Subject: Re: PVC glazing
From: "Loren"
Date: Thu, 11 May 2000 19:54:44 -0500
Tougher Yes, but much pricier isn't it. The PVC was cheaper than $1/sq.ft.
I've not found Lexan that cheap.
Loren
http://paisite.com/sunlife/index.htm
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> From: William Evans
> To: aquaponics@townsqr.com
> Subject: Re: PVC glazing
> Date: Thursday, May 11, 2000 3:36 PM
>
> Loren wrote:
> >
> > Does anyone have experience with PVC glazing?
>
> what about polycarbonate-lexan- tuffer stuff i think than PVC
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Subject: Re: PVC glazing
From: William Evans
Date: Fri, 12 May 2000 17:32:35 -0700
Loren wrote:
>
> Tougher Yes, but much pricier isn't it. The PVC was cheaper than $1/sq.ft.
I think a 12 foot length by 2 1/2 feet wide is in the 20 dollar range.
Of course this is just for "patio cover" not double wall poly carb
glazing that's at least 40 bucks a sheet. Id weigh the toughness issue
carefully and shop thru a dedicated greenhouse supplier to get what you
really want, choice is limited at the homecenters., to be sure.
The lexan is very duraBLE, Ive had corrugated lexan panels go sailing
over the roof,landing 40 feet away ( santa ana winds here in san diego)-
never broke or cracked one.
bill evans
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Subject: Re: PVC glazing
From: Sojourner
Date: Fri, 12 May 2000 20:36:02 -0500
William Evans wrote:
>
> Loren wrote:
> >
> > Tougher Yes, but much pricier isn't it. The PVC was cheaper than $1/sq.ft.
>
> I think a 12 foot length by 2 1/2 feet wide is in the 20 dollar range.
> Of course this is just for "patio cover" not double wall poly carb
> glazing that's at least 40 bucks a sheet. Id weigh the toughness issue
> carefully and shop thru a dedicated greenhouse supplier to get what you
> really want, choice is limited at the homecenters., to be sure.
> The lexan is very duraBLE, Ive had corrugated lexan panels go sailing
> over the roof,landing 40 feet away ( santa ana winds here in san diego)-
> never broke or cracked one.
> bill evans
Double wall 6mm polycarbonate is $1.65 per sq. foot here:
http://www.sundancesupply.com/index2.html
If by "PVC" you mean regular old plexiglass, letting yourself be swayed
by the fact that its cheap is a false economy. It scratches, it gets
brittle, it yellows, it shatters.
Polycarbonate is what I'm using for my attached greenhouse. There's a
guy who built a dome of it 20 years ago and its still going strong.
It's warranted for 10 but actually lasts longer.
They have a minimum $500 order, and there is a crating fee ($7 x length
of the longest sheet of polycarbonate you are buying, minimum $49)
I have NO idea what shipping runs, it comes freight from either
Wisconsin or PA, whichever is closest to you I would assume.
If you can find a supplier close to you then go for it. I've not been
able to locate anybody in my area who carries the stuff.
--
Holly ;-D
Contrary Peasant
sojournr@missouri.org
If you see the Bhudda by the side of the road . . .
give the poor slob a lift, his car probably broke down.
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