Structurally, that's going to be very difficult. A square or round tank will be easier. For instance, I have a cistern outside my garden gate which is just two pallets and two 4'x4' pieces of plywood, lined with a big scrap of greenhouse plastic. It makes a 4'x 3.5'x 3.5' deep tank. The plywood bows out and the pallet boards bend, but they're holding, and have done so for several years now.

I wonder if three or four of these would work for you, instead of one long one.

Also, I used to have a cistern in my shade house (back before I took down the shade house) made of six pallets, banded together into a hexagon with some stainless cable (old boat mast stays from the dump), lined with scrap carpet to smooth out the sharp corners, and then lined with greenhouse plastic. That worked well too, and was cheap.

Originally, I had a blue tarp for a liner. It lasted a year and looked like this:

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Dan

I didn't use wood. I used wire and fanfold insulation to make a 8 foot diameter tank ~ 4 foot deep (roughly 1500 gallons).

Cost was less than $100
- wire mesh fencing
- Fanfold isulation
- GH poly film (used) (i.e. no cost)

Still needs some finish touches...

Poppa
P.S.
I meant to add a tarp layer but forgot. DOH! doesn't seem to need it. Just need to be extra careful.

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A rectangular one will be difficult to handle hydrostatic pressure structurally.

A round one like poppa's is a very good way.

dcarch

Homer, I mean poppa,

I like very much.

How thick is the Fanfoam?
What type of wire fencing? Does the fencing wrap under the bottom. What holds the ends together to form the cylinder?
Between witch layers was the tarp going to be.
In the first photo, are those pieces of 2x4?

What do you think the life expectancy will be?

3.142 x 48sq x 48 = volume Something wrong with my math

Eric

3.142 x 4sq x 4 = 201. x 7.48 = 1504 gallons ????????

Eric

Hi
When you say "fish tank" do you mean to heat and filter it?? I keep a 5x10 made of stacked 4x4's lined with a fiber glass tarp .is certainly showing it's age but has been there since 82. I use it mainly as a grow out for tropical fish and for rain water storage .
A good choice for the money is stock tanks. Poly over metal but that depends on the fish gary

I think I've got it.

Make end walls out of plywood, reinforced with 2x4. They're easy.

The 12' sides are supported by vertical 2x4, which are wired together at ground level, and held together at the top with wire, which runs through the air above the water surface. Just add a plywood fence within the posts, then your pond liner, and then (as the texas joke goes) fill it with water.

Here's a guy building a birchbark canoe. It's the same idea. Vertical poles tied together over top of the "tank".

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Dan

Gary,

It will be used for Talapia in aquaponics set up. I've seen the stacked 4x4 and landscape timber design.

Round tanks would be easier and cheaper to build, but they don't use the space efficiently.

Dan, cool picture. I know someone who build wooden kayaks.

Eric

The round geometry reduces the extra pressure in the sides. It is indeed a creator of unusable space, but the headache of leaks-repair will be reduced. That's why water towers and big storage tanks for water and oil are round (who sez all that math was wasted, huh?).

Dan

Dan, (who sez all that math was wasted, huh?).

What?

I was trying to figure out how Poppa came up with 1500 gallons.

Is the math correct????

Eric

pi*r^2*depth= 3.1415927*4*4*4= ~200 cubic feet = 1500 gallons.

Dan

Your loading should be a little less than 400plf. Span is 12'. The pressure treated lumber I use in home construction is yellow pine. Build a girder with 2-2x12, nailed with 4-16d sinkers at 12" o.c. You should get by with a single 2x12 at top and middle. Bolt w/ 4- 1/2" bolts at corners. You can add a stiffback at the midpoint and cable across at top and bottom.

Mark

I meant my physics way back when - we used to do questions like these to understand why tanks were round, hopper cars were that shape, LNG was shipped in that shape, The end of rockets and fire extinguishers were cone-shaped, yada. More fun than hydro. Your formula for volume looks fine to me. You can use the space in the curve to do something useful or put the pump in that volume.

Dan

The minimum surface area to enclose the largest volume is a sphere.

The minimum lineal length to enclose an area is a circle.

With a circle, you can use steel cable to counteract the hydrostatic force, and steel is very strong in tensile strength.

dcarch

Eric...

The fanfoam is standard stuff for underlayment under siding. You can get it at one of the box stores. Roughly 3/8"?

The wire, also standard at the box stores is fairly heavy gage and the openings are roughly 2" x 3 ". I bought a 50' roll which will make 2 tanks.

To join the ends, i cut the wire so i had an inch long tang on each vertical wire, on both ends. I overlapped so the last vertical wire on each end lined up with the second Vertical wire on the opposite end. then i wrapped the tang around the corresponding horizontal wire after the second vertical wire. That was fun to write and if you understand it you must be drinking. Here's a picture though i am not sure it helps!!!

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The fencing does not run under the bottom.

The 2x4 s were just used to weigh down the bottom while i played and were removed before adding the liner.
I thought o adding the tarp between the wire and the fanfold. I was coincerned that the water pressure might force the fanfold to push through the wire. Doesn't look to be an issue at all.

FYI, i went with the round tank because i could make the bottom conical to help with solids removal.
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The life expectancy will be slightly shorter than whichever of my kids puts a hole in it. I have no idea how long the fanfold will last. That should be the limiting factor if not punctured i would guess. Thinking UV, but i am uncertain how much actually gets into the GH.

Volume of a cylinder is Radius squared times Pi time depth. Don't forget you need to convert the cubic feet to gallons, roughly 7.5 gal in a cu ft so 200.96 x 7.5 = 1507 gallons

poppa

That was fun to write and if you understand it you must be drinking. Here's a picture though i am not sure it helps!!!

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I'm thinking the only Tang I should be drinking is Tang. It's not just for astronauts you know. No I followed along just fine. The picture also tells a thousand words.

How will you plumb between the two tanks. Will a regular through wall fitting work? The GH plastic and Fanfoam don't seem strong enough.

Tanks a lot
Eric

They will be separate systems.

I plan to have a center post in the tank that sucks up the water from the bottom center of the tank into, well... something! Nothing through the walls.

For those of you who do not want to go thru the trouble of building one, an above ground swimming pool is not outragiously expensive. Some even come with complete plumbing system.

Check Craigslist, you may get one for free.

dcarch

On occasion, here on the Island, people giving away above ground hot tubes. I think they would be perfect. Insulated, plumbing, pump, aerator. Basically ready to go.

What do you think about this idea.

Eric

Mark,

Can you give me a little more detail. More information on the girder. Is it just a double layer of 2x12 nailed every 12. Sound more like a header or beam. Do you have a way to post a rough sketch of your whole idea?

Poppa,

How much force can you apply at the top of your cylinder. If you lean against it, will water pour out? Will it hold up to everyday dealing with fish and plants.

Eric

Eric, the water pressure at the top is very little. Think about an above ground swimming pool... there's a reason it has the frame around the rim... it's not just for walking on, it would be very easy to push the side in along the top.

I won't be building a full frame, but i do need something to suspend my central drain from, so i imagine there will be at least on brace to lean on when working in the tank.

I got the idea from a thread at bakyardaquaponics.com where someone with a low cost facility in africa had built one. There's even a commercial version where the lower third of the tank has wires spaced twice as close. That's one reason i decided to sink mine in the ground a foot. If it's going to give it would be at the bottom. Thinking about that, i may add a kickplate where i will tend to stand. lol.

Eric,

I'm computer illiterate so I'm not sure how to do that, especially since my scanner quit working. As poppa says, the greatest pressure is at the bottom. I design and build homes and I went to my design tables for wood construction. My tables are for white woods and you should gain some 25-30% with yellow pine or doug fir. I didn't dig my books out to size the beam for those species, so 2- 2x12 is probably overkill.

You would nail them together as you would a header or floor girder. Of course they'd be attached perpendicular to the sheathing.You'd run the corners past each other and one beam over, one under then bolt them. Without digging out my APA books I'd say 3/4" sheathing would more than suffice.

Frankly, a round tank might make more sense because the wood framing at the exterior of the tank will eat up 12"all around your tank. You should block between the framing members at all corners and at mid-span. Top member could be a 2x8- only 9" of pressure against it.

Just like building a floor vertically, really.

Mark

There's a guy on craigslist that is selling these containers. $80.00 each and hold about 250 gallons. 4 or 5 of these could work.

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What do you think

Eric

What was in them?

Dan

Soy something or another. Anyway food grade plastic.

They have valves close to the bottom. Would make plumbing easy.

Eric

I like those, but would the fish? Seems small from here for tilapia. Other fish for poop, sure...

Dan

Eric,
Many people (including me) in this area haul their domestic water and I've seen those tanks several times. Bigger ones would be ideal.

I've checked out a few youtube videos on the aquaponics topic and they say tilapia require minimal space to thrive. One guy introduced a pump to create a current which forces the fish to swim into it. He said it made better quality fish flesh. It's an idea that would require some space but would be fun to experiment with.

The hydroponics shop in Pagosa Springs, Co. has a small aquaponics setup for sale. A container for plants sitting on top of a fish tank. It wasn't very big and was quite expensive. The fish tank was maybe 40 gallons.

Interesting concept though.

Mark

Mark, I think when they state 'minimal space' they are talking about stocking density. Having a larger tank would cut down on the number of times you have to change the water (where Eric is there are strict limits on runoff/septic, as Hood Canal and the Sound are slowly being choked by human effluent).

At least, this is what I remember when I researched all this to consider homesteading in the Osoyoos-Selkirks some years ago now.

Dan

Eric,
You and I are almost exactly on the same page of research and development for the aquaculture part of an aquaponics system. I am trying to figure out the best way to have two 2'x8'x36" tanks on either side of a 12'x26' shed (four total tanks). The shed will be adjoined to a 20'x 52' greenhouse. I just wrote quite a bit here about the subject but it was deleted before it was submitted. I would really like to share notes with you about our strangely similar tank research. You can email me directly at emailtreymon@yahoo.com. By the way, I had NEVER seen or noticed those soy/water/whatever tanks before either until recently I saw a guy on youtube making smaller aquaponics systems out of them... now I seem to see them all over town behind restaraunts and such. Pretty cool but not what I need. Thanks for starting this blog! Later, -Trey

For a real world view of using aquaculture and hydroponics in a conjunction google E&T Farms in West Barnstable, Massachusetts. They raise talapia, Koi and bass in linear flow through ponds. The water is recirculated through the hydroponic fields. Biological filtration converts the ammonia waste to Nitrite, Nitrite is converted to Nitrate and the nitrate feeds the plants.

For tanks you should consider separating it into 4 to 6 or more smaller tanks. Fabseal does seam welded PVC liners that are drop instalaton or line with EPDM.

That is a lot of water to move, pumps will be expensive.. consie air lifts to do your water movement.

Bill