Aquaponics Digest - Mon 02/09/98
Message 1: More on algae v. pellet feed
from John Shannonhouse
Message 2: Aquaponics
from S & S Aqua Farm
Message 3: self-sufficient homestead
from jmsutton@atl.bna.boeing.com
Message 4: Re: self-sufficient homestead
from S & S Aqua Farm
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Subject: More on algae v. pellet feed
From: John Shannonhouse
Date: Mon, 9 Feb 1998 12:25:56 -0600
Hello,
I was thinking more about the experiments that James Rakocy
described. It does seem that algae is inferior to pellet feed (a 3- to
5-fold growth difference). The experiments prove that as long as cheap
pellet feed is available, pellets are superior to algae as food. I would
not discount algae's value as a food source, however. There are a number
of variables that are not controled, in my opinion. Then again, I'm no
aquaculturist; I may be making some obvious mistakes (if I am, please point
them out). The variables are:
1) Continuous (algae) v. periodic (pellet) feeding:
How often do the Tilapia eat when they have food around all day?
>From what I read about Tilapia, their digestive systems take awhile to get
going. They need to lower the pH of the first stage of their digestive
system (I forget the term used, and I don't have the book in front of me)
to around 2. As a result, when the fish are fed algae, the first of the
algae they ate were not digested because their cell walls were not broken.
As the Tilapia digest their food, they must raise the pH as it travels
through their digestive system. All of this takes energy. If the Tilapia
are feeding continuously or taking in a relatively small amount of food
many times per day as opposed to larger quantities of food a few times per
day (when they are fed pellets), they will be spending a lot more energy
running their digestive system and thus less energy growing.
(Was edible detritus available to the pellet-fed Tilapia?)
2) Eating small algal particles v. pellets:
It was not clear if you were including this point in your previous
post (as opposed to point #3, which you did cover). I don't know how large
the pellets are compared the the algal fillaments, but I suspect that the
pellets are smaller. That means that the fish need to swallow more water
with their food to eat the same mass of algae as a food pellet. Not only
is the algae itself more hydrated than the food pellet, but the fish must
deal with more water. It needs to lower and raise the pH of that water
(see point #1) and to feed for a longer period of time with each feeding,
costing the fish more energy.
3.) Hydration of the food:
A given mass of pellet has more dry mass (thus more available
energy) than the same mass of algae. Then again, a dried pellet may not be
a fully utilized as a hydrated algal mass (picture clumps of pellet pieces
passing through the digestive system with only the outer parts of the
clumps being utilized because the componets don't get fully solublized).
The overall amount of nutrition gained from the pellet is probably higher,
though.
4.) Composition of the food:
What nutrients (if any) are limiting in Tilapia growth with
commercial feeds? Has anyone found a mineral, vitamin, amino acid, etc.
can be added to algae-based feeds (if any exist) that increases growth
rate? It may be possible to add a cheap supplemental feed pellet to
algae-fed fish that significantly increases their growth (if one or a few
nutrients are limiting).
An experiment that seems fairly simple to me is to make a series of
feed pellets out of algae, commercial formula and algae/commercial formula
mixture with various degrees of hydration (dry weight varying from as low a
percentage as you can get it up to >90%) and see how quickly the Tilapia
grow on each diet.
As far as costs go, raising and harvesting algae might be more
expensive than buying commercial feed (especially on a small scale). Keep
in mind that when raising algae for fish feed, you don't need to keep the
same standards of purity that you need for human food (health foods such as
Spirulina and Chlorella).
John Shannonhouse
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Subject: Aquaponics
From: S & S Aqua Farm
Date: Mon, 09 Feb 1998 14:07:18 -0600
Dear friends -
Having spent the last few days updating records and reviewing some of the
letters/e-mails we've received directly, I'm reminded of the tremendous
variety of needs, plans, proposed uses, sizes of operation, locations,
interests and "experience" levels expressed by those who've written us -
many of whom have joined this list very quietly.
I would encourage those of you with questions to remember that this list is
provided for all of us to share, question, and learn. As long as it relates
to "aquaponics" and related items, all comments and questions are welcome.
Hope to hear from you soon.
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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Subject: self-sufficient homestead
From: jmsutton@atl.bna.boeing.com
Date: Mon, 9 Feb 98 9:18:23 EST
Thanks for the encouragement to participate. I just joined this list, so
I have a few questions.
1) Is there an archive of old messages somewhere, so I don't bore
everyone with questions they've already answered several times?
2) I'll be building a self-sufficient homestead shortly, and my concerns
relate to that instead of to commercial production. For instance,
how long can you store pellets (if you wanted to store them just as
you might store food for an extended personal or societal lean time)?
Any other comments about aquaponics in a homestead setting?
3) What's the best-value source for pellets? What about in the Southeast
(I live near Atlanta)?
4) I assume you've already talked a lot about raising your own "input
food" for the fish--as opposed to buying commercial feed. Can you
point me to any info on the practicality and requirements of "growing
your own?"
Thanks for any help,
James Sutton
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Subject: Re: self-sufficient homestead
From: S & S Aqua Farm
Date: Mon, 09 Feb 1998 19:13:31 -0600
At 09:18 AM 2/9/98 EST, Jim Sutton wrote:
>Thanks for the encouragement to participate. I just joined this list, so
>I have a few questions.
>
>1) Is there an archive of old messages somewhere, so I don't bore
> everyone with questions they've already answered several times?
SHAME on the list provider (who still has not learned how to provide the
archive file on a web page). I'm sorry to say that the only official
archive to date is still in my computer. Time has a way of being so
insufficient, especially this time of year.
We've discussed many topics on this list since November, and if you have a
specific subject area, I'll post the thread directly to you (or to the list
if requested). Also, if you were to ask a question that had been covered in
depth in earlier posts, I'll try to pull the older posts and send them
along. I'm truly sorry not to have this accomplished yet.
>2) I'll be building a self-sufficient homestead shortly, and my concerns
> relate to that instead of to commercial production.
We participate (mostly lurk) in a wonderful homestead group. I'd be happy
to send you the subscribe info if you want. I don't know where I've found
more useful knowledge all in one place on the internet.
For instance,
> how long can you store pellets (if you wanted to store them just as
> you might store food for an extended personal or societal lean time)?
> Any other comments about aquaponics in a homestead setting?
>
>3) What's the best-value source for pellets? What about in the Southeast
> (I live near Atlanta)?
>
>4) I assume you've already talked a lot about raising your own "input
> food" for the fish--as opposed to buying commercial feed. Can you
> point me to any info on the practicality and requirements of "growing
> your own?"
We've had quite a bit of conversation about alternatives to commercial feed.
I know several list members are actively pursuing feeds that can be
qualified officially as organic. Perhaps one of them can respond to this
question. IMO we've not actually resolved this topic, but I'll try to post
the older correspondence to you tomorrow (and anyone else new to the topic
who wants it).
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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