Aquaponics Digest - Sat 03/14/98

Message   1: Aquaculture Research Specialist II,  University of the Virgin
             from "Damon R. Lesjack" 

Message   2: Re: Pentagonal polyhouse
             from Ian Beaver 

Message   3: Re: Greenhouse structures
             from crystal 

Message   4: Animals in the greenhouse (wasRe: Introduction)
             from Gordon Watkins 

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| Message 1                                                           |
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Subject: Aquaculture Research Specialist II,  University of the Virgin
From:    "Damon R. Lesjack" 
Date:    Sat, 14 Mar 1998 08:35:07 -0400


DEADLINE DATE: April 1, 1998

POSITION TITLE:  Research Specialist II - Aquaculture,  University of
the Virgin Islands, St. Croix, U.S.V.I.

ASSIGNMENT:  Under the direction or the Aquaculture Program Leader,
the individual will conduct research on tilapia production in
recirculating greenwater tank systems, including engineering design,
water quality management, effluent treatment and land application of
effluents for plant crop production, and will assist with ongoing
projects on aquaponics and fingerling rearing in recirculating
systems. The individual will be responsible for supervising a water
quality analyst, maintaining research facilities and equipment, grant
writing, planning and initiating experiments. Collecting and
processing data. Preparing publications, presenting papers at
conferences and providing aquaculture training.

QUALIFICATIONS: Candidate must have a Master's degree in
aquaculture and successful work experience in the area of research
dealing with the culture of tilapia. Candidate should have knowledge
of tilapia culture systems, field research techniques, statistical
procedures, and data processing with microcomputers. Knowledge of
aquaculture literature. Good writing ability and experience with
training and extension are desirable. The position requires a highly
motivated individual who is able to work as a team member with people
of diverse backgrounds.

COMPENSATION AND FRINGE BENEFITS: The salary for this professional
staff position is from $26,978 to $37,904 for the > administrative
year, depending upon qualifications and experience. Benefits include
21 working days of annual leave, 15 working days of sick leave, a
liberal TIAA-CREF or Virgin Islands government retirement plan, as
well as comprehensive group medical and dental insurance program.

APPLICATION PROCEDURES: Letter of application, up-to-date resume,
official college transcripts, and three letters of recommendation
should be addressed to: Dr. James Rakocy, Research Director.
Agricultural Experiment Station, University of the Virgin Islands, RR2
Box 10,000, Kingshill, St. Croix. U.S.V.I. 00850.


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| Message 2                                                           |
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Subject: Re: Pentagonal polyhouse
From:    Ian Beaver 
Date:    Sat, 14 Mar 1998 08:52:59 +1300


I have had a number of replies to my post, regards the pentagonal
polyhouse idea. Sorry, I dont have any plans, since I wiped them out to
make more room on my hard drive, silly me.

On the subject of size, these units can be made to any size one desires,
though there are engineering limits to this. The size is totally
determined by the size of the 25 members that you make them out of.
Changing the size of the member changes the volume of the unit. The
first one I made had members of 2400mm (8ft) but this, in my opinion was
too large, since the size of each triangle was to big and caught too
much wind, for the strength of the plastic sheet. I have since downsized
this house to 2000mm, and that works well.

I have another one that is 1800mm members and is covered in netting, as
a trellis frame for passionfruit. Inside this house is a really nice
shade shed, using the passionfruit as the covering.

The trick with making these things is how one goes about joining them
together, since each junction has up to 5 members arriving at that
point, as a five sided star. How I acheive this is to drill the end of
each member and insert a peice of 12mm*5mm steel, about 100mm long, each
peice of steel has a 6mm hole drilled in it. The steel key is hammered
tight into the hole in the end of the member and members are then
assembled into the dome, by bolting them together with a 6mm bolt. This
is the basic constructional idea.

If one was using steel framing, the steel could be bolted or small tags
welded to the end of each member. You need to be careful, not to have
any protrusions sticking out that will cut the plastic.

Each of the 25 main members is idential in length, and it pays to keep
this length as accurate as possible, since the truer the structure, the
better the plastic will fit, when it comes to covering.

Note that the unit has a foundation ring of 5 members, and another ring
of five at shoulder height, I call this the top ring. There are ten
members make up the walls and five more, the roof. 25 in all.

I premake all 25 members, cutting the timber to length, drilling the
ends, making up the steel key pegs, inserting them into the drilled
holes and bending them to allow the angles to meet. I can provide more
details of these angles, if anyone really wants to make one. I'd need to
make some sketches and scan and send. There is a bit of work in making
up the members, but assembly is rapid. (like 1 hour or less).

I start assembly, by drawing out a pentagon on the ground, and digging
five holes and inserting five foundation posts and concreting them in.
(usually about 600mm deep). These posts come just above the ground
level. You need to take care that the tops of all posts are level with
each other and that they represent a true pentagon.

Next I take five premade members and assemble a pentagon, on the
ground,  as a ring, leaving the bolts loose. Ill call this the
'foundation ring', or bottom ring. Its better to assemble on a flat
peice of ground and move the whole thing onto its foundations when it is
completed, rather than trying to assemble it onto the foudations. The
reason for this becomes obvious if you try.

I then assemble one triangular wall section onto one of the sides of the
foundation ring, by adding two more members. Then a second wall section,
adjacent to the first, by adding two more wall members. At this point
you connect the two wall sections, at the top, by adding the first
member of the top horizontal ring. You will need a couple of helpers to
hold things whilst you put it together. Continue this process, adding
wall members and top ring members, until you get back to the starting
point. You need to take care, not to bend the steel pegs at this point,
since the whole structure is floppy and can easily fall, but a couple of
extra hands will take care of that.

Then comes the fun part, adding the roof sections. You need to make a
stand, I use 200l drums or a ladder, so that can get you high enuf to
reach the apex. Add one roof member at a time, working around the
pentagon until the last one bolts in place. The units suddenly becomes
rigid and strong. (as an aside, you can swing from the apex of these
structures, no worries).

Move the whole thing onto its foundations, and wire or strap the frames
to the foundation posts, to prevent it blowing away in the wind. (I know
one guy who neglected to do this and his unit ended up in the
neighbours, like a tumble weed).

Note at this point that I am describing how to make the basic frame,
without a door, or ventilator.

At this point you can cover in netting, or perhaps shadecloth, onto this
simple form of frame. If its a plastic house, then you need to do a bit
more construction. The wall sections simply wrap around this frame,
between the upper and lower pentagonal rings, straight off the roll.
(Beleive it or not)

I just staple onto the wooden members, which is the great benefit of
wood. How one would attach the sheeting to steel frame is anyones guess.
BTW I use preserved or H3 tanalised wood, so that it wont decay with
damp. (The H3, represents the degree of preservative in the timber)

The roof is made of five triangular panels, and is covered in two
peices, one covering three consequtive panels and the other peice, two
panels. They wrap on in the same way as the walls, just they are shorter

If you are using plastic sheeting, then care needs to taken, to ensure
that the top sections overlap the bottom, so that the water runs off OK.
I fold a seam into all plastic edges for greater holding, putting a
staple at every 100mm or so.

When fitting the plastic, you need to tension as you go, and if youve
got the frame accurate, the plastic fits like a glove, and will last a
few years, no problem. My first house is made with cheap, non UV
protected, poly sheet, 125 micron, and has done three seasons already.
On later houses I have used UV stabilised, more expensive, horticultural
film, but care needs to taken to make sure the UV protective coating is
on the outside.

Now to make a door way. There are probably a number of ways to do this,
but Ill describe how I do it. I use a 600 wide door, made from the same
50*50mm wood. What becomes obvious, once the frame is up, is that the
walls are all sloped. Half of the wall panels slope in and the other
half outwards. I make my doorways in a panel that slopes in at the
bottom. Bearing in mind that the frame is already assembled and tied to
the foundation posts, it is now possible to remove one of the bottom
ring members.

I now cut two vertical peices, that drop from the wall members on either
side, 600mm apart, and go vertically into the ground, to form the door
frame. I usually use a heavier timber for these and of a material that
is OK to be in the ground without rotting. I use H4 tanalised pine for
these, usually 100*50mm. This is where the compound saw comes in, since
where these uprights meet the wall frames is a complex, compound angle.
Once you have the angles, it is easy to set the saw to make more. These
posts are then cemented into the ground.

Since you have removed one bottom ring section, it is now necesary to
add two small sections, on either side of the doorway, back to the
founadtion posts, to take the bottom side of the plastic.

You are now ready for the plastic sheeting. Start at one side of the
doorway and work around, coming back to the other.

For doors, I make up a wooden frame of 50*50mm that fits neatly into the
door hole and is hinged onto the vertical posts just described. Note
that the door is a square at the bottom with a triangle top. I hold my
doors together with metal strapping applied to each side of each timber
junction, this make a good strong door, but again it has compound
angles. (such is the joy of working with angular structures, curse that
bucky fella). I then cover the door frame with plastic.

Now the ventilator. The obvious place to put a vent is in the roof apex,
but this is difficult, so I put them in a wall section instead, opposite
the doorway. As a vent flap I use a 250mm peice of timber, about two
metres long, laying horizontal, and hinged off a top ring section. I add
another horizontal member between two wall members, 250mm below the top
ring. (compound angles again) This makes a frame into which the vent
flap is fitted. The flap itself has angles at the ends to fit this hole.

So thats about it, sounds tricky I suppose, and probably not a project
for someone without construction skills. The first one is the most
difficult. However, the results are practical, interesting and very eye

Another point is that if you make your foundation posts a bit higher and
lift the whole thing off the ground, you can build a solid wall around
the bottom, possibly with a cement floor. This could be great for beds,
whether they be hydro/aquaponics media or organic whatevers.

Mine are all set up with a keyhole garden design, where you have a
walkway into the centre of the house, and the beds are all around the
walls. This is very efficient from a space utilisation point of veiw.

One point was made, as to the possibility of adding insulation. I have
only a single skin, but see no difficulty with adding an extra skin
spaced away from the first by adding an additional spacer frame to the
main frame, then placing a second layer over the outside. 

About the angles, these arent as difficult, once you realise that there
are a few basic angles involved, and that these same angles repeat,
however I saw soemone try to make one with just a hand saw, and the
result was not good.  I personally, only have a simple drop saw that
only cuts a single angle, and I use jigs to get the compound.

Good luck

Ian Beaver
Northland, New Zealand

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| Message 3                                                           |
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Subject: Re: Greenhouse structures
From:    crystal 
Date:    Sat, 14 Mar 1998 19:18:42 -0800

.       * Does plastic traps infra-red better than glass? 
        * Is this related to ambient temperatures?
          (Esp in autumn and winter)

On a related note...

        * What do indoor greenhouses use to raise ambient temperatures/

Best Regards,

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| Message 4                                                           |
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Subject: Animals in the greenhouse (wasRe: Introduction)
From:    Gordon Watkins 
Date:    Sat, 14 Mar 1998 21:26:38 -0600

Welcome to the list, Jim.
        I assume you're speaking of gaseous ammonia and not the dissolved kind
produced by fish.
        Anna Edey, who created Solviva greenhouse on Martha's Vineyard, devised
an interesting way to remove ammonia from the atmosphere of her gh.
During the winter, she kept chickens, rabbits and goats in an attached
shed/stable on the north side of her solar gh, separated from the
growing area by a "water-wall" which absorbed the heat generated by the
animals as well as solar radiation from the gh side. Besides heat, the
animals also contribute CO2(a valuable plant nutrient), but when she
vented the stable air directly into the gh she had ammonia burn on the
plants. She then came up with the ingenious "earth lung" in which the
stable air was vented into coarse rock beneath a dirt growing bed. As
the CO2 laden air percolated up through the soil and into the gh
atmosphere, the ammonia was absorbed by a nitrogen-loving crop like
beets, which was later sacrificed to the compost pile. With this system,
she successfully combined animals and plants in a gh.

dbell wrote:
> some were I heard that that mixing animals and plants in a greenhouse
> doesn't work because the urine produces ammonia which the plant can't
> tolerate.
> Thanks for listening and hope to hear from some of you soon
> Jim

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