Aquaponics Digest - Sun 03/26/00
Message 1: Re: Any suggestions
from Chris Weaver
Message 2: Re: Well on my way to becoming a fish farmer
from "TGTX"
Message 3: Re: Well on my way to becoming a fish farmer
from "TGTX"
Message 4: RE: Well on my way to becoming a fish farmer
from "Ron Brooks"
Message 5: turtles
from "timjohanns"
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Subject: Re: Any suggestions
From: Chris Weaver
Date: Sun, 26 Mar 2000 07:04:08 -0500
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Sam Levy wrote:
> >I assume that this is fairly representative (they mention a density of
> >80kg/M3 which seems higher than most)?
I have found that the growth represented in the Aquasafra chart is an excellent
representation of growth to be expected. I have had better and worse(not
often) growth in some lots, but on average they do the same or better than
Aquasafra. P.S. I haven't bought fry from them in over two years, so it isn't
a personal thing I just use the chart as a tool to evaluate my own growth.
> 80 kg/m3 is 0.67 pds/gal--and is a high rate--although if it were one tank
> out many & market ready (and being sold) at that density, it might be ok.
> (jim's comments on feeding quantities for the whole system actually cvers
> this uite nicely)
With most recirculation Tilapia farms located in northern areas, we try to
attain 80 kg/m3 as a minimum. I run my system at 75 kg/m3 max for fry up to 50
grams and then 80-120 kg/m3 for grow out.
> also, if you calculate any of the growth rate parameters (say sgr) for each
> week, i think you'll discover that the rate of growth is far greater in the
> smaller animals than in the larger ones & that the absolute rate of growth
> (grams/day, for instance) will be larger in the big fish.
>
> if you check your feeding, you'll probably find that about 50% of the total
> feed will be presented in the final third (time wise) of growth.
>
> sgr can be calculated as: ln(wo/wi)/t
> where wo = final period weight
> wi = initial period weight
> t = time of period (days)
>
Specific Growth Rate is an excellent way to track the growth of fish.
>
>
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Sam Levy wrote:
>I assume that this is fairly representative (they
mention a density of
>80kg/M3 which seems higher than most)?
I have found that the growth represented in the Aquasafra chart
is an excellent representation of growth to be expected. I have had
better and worse(not often) growth in some lots, but on average they do
the same or better than Aquasafra. P.S. I haven't bought fry
from them in over two years, so it isn't a personal thing I just use the
chart as a tool to evaluate my own growth.
80 kg/m3 is 0.67 pds/gal--and is a high rate--although
if it were one tank
out many & market ready (and being sold) at that density, it might
be ok.
(jim's comments on feeding quantities for the whole system actually
cvers
this uite nicely)
With most recirculation Tilapia farms located in northern areas, we try
to attain 80 kg/m3 as a minimum. I run my system at 75 kg/m3 max
for fry up to 50 grams and then 80-120 kg/m3 for grow out.
also, if you calculate any of the growth rate parameters
(say sgr) for each
week, i think you'll discover that the rate of growth is far greater
in the
smaller animals than in the larger ones & that the absolute rate
of growth
(grams/day, for instance) will be larger in the big fish.
if you check your feeding, you'll probably find that about 50% of the
total
feed will be presented in the final third (time wise) of growth.
sgr can be calculated as: ln(wo/wi)/t
where wo = final period weight
wi = initial period weight
t = time of period (days)
Specific Growth Rate is an excellent way to track the growth of fish.
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Subject: Re: Well on my way to becoming a fish farmer
From: "TGTX"
Date: Sun, 26 Mar 2000 08:18:40 -0600
> Sam I normally operate O2 at 8 And all the clocks were running fine , no
> loss of time. I now have a few more fish swimming sideways :( My biggest
> males except for 3 are now in the freezer and another one of those is
> swimming sideways tonight. My system is clearwater Ricirculation and the
> only thing that has happened is 4 days ago I did a 50% water change
Ron, what exchange rate are you operating your system under? How many tank
volumes per day were going through the biofilter at the time of the
mortalities? Could it be that the ammonia production rate exceeded the
nitrification rate because of insufficient tank exchange rate?
Or, could the 50% water change have diminished the biofilter's and/or water
column's nitrifying bacteria population, thereby increasing ammonia
concentrations? If the water change involved chlorinated potable water,
that might be a consideration. If it definitely wasn't low O2, then maybe
NH3?
If not water quality, could it be Aeromonas or Edwardsiella, or some other
introduced opportunistic bacterial pathogen from the outside water brought
in to do the 50% exchange that affected the swim bladder and stress the fish
to the point of eating the big Chalupa?
Just a thought or two.
Ted
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Subject: Re: Well on my way to becoming a fish farmer
From: "TGTX"
Date: Sun, 26 Mar 2000 08:24:22 -0600
One more thought: Is the 8ppm DO2 standard potentially higher at times?
That is does it ever, or could it have ever, at any time/condition of
day/night/salinity/temperature become any more than 100% gas saturation for
your system? If the DO2 is from pressurized/or plunge pool aeration with
air into deep water or pressurized pipes (N2 +O2), then supersaturation can
take place some times If so, could your fish have been showing gas bubble
problems?
Ted
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Subject: RE: Well on my way to becoming a fish farmer
From: "Ron Brooks"
Date: Sun, 26 Mar 2000 19:01:30 -0500
Ted
Well I have total turnover of all the tanks every 2.5 hours.
One of the tests I was unable to do was O2 due to the reagents not working ,
I guess I should have ordered new , the old stuff must have been to old.
Ph was 7.4
ammonia 0
Nitrate 1
nitrite .5
I did notice that the water coming out of the biofilter yesterday was quite
foul when I started to break the system down. So I think it was starting to
crash
Ron
-> Ron, what exchange rate are you operating your system under?
-> How many tank
-> volumes per day were going through the biofilter at the time of the
-> mortalities? Could it be that the ammonia production rate exceeded the
-> nitrification rate because of insufficient tank exchange rate?
->
->
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Subject: turtles
From: "timjohanns"
Date: Sun, 26 Mar 2000 19:52:19 -0800
having some problems with the turtles biting tails, like.. off, now that
they are getting larger, noticed that feeding them more frequently curtails
this. We are building tanks for hatchlings out of 4x8 sheets of recycled
plastic 1/2" thick, with 8" sides. these run about 80.00 per sheet so the
tanks are cheap and will last until the next set of dinosaurs rule the
earth, we put silicone in the joints prior to screwing them together every 4
inches. they hold water but we're thinking of welding them with a plastic
welder like body-shops use to repair plastic car parts, to enhance their
strength, we think they will work for bio beds as well if used in
conjunction with structural support, be it wood or metal tubing frames.
anyone know of a bamboo variety that could grow in zone 4? would like some
for garden grids and water garden crafts, etc. sources? web sites? phone
#'s?
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