How to build a 8' x 3' x 3'

ali12345 · Post by **ali12345** » 22 Oct 2006, 16:36

Hi,
I have a space available and I'd like to build a brick pond with a glass front. Has anyone done this?
thanks
Alison

apistomaster · Post by **apistomaster** » 22 Oct 2006, 20:25

I have never built a tank of the type you plan but I do have some advice. This will need steel reinforcing bars incorporated into the design to deal with the flexural stresses involved. Brick and mortar are strong in compression but weak in tension.
I am a retired structural construction inspector with 27 years experience in USA earthquake zones 3 and 4 high rise construction. The structures in these areas require special designs to make them more earthquake resistant than anything being built in the UK. Still, water weighs the same wherever you are and more than a few have learned the hard way that they have underdesigned their home built aquariums. One can build the same sized tank out of plywood,screws, epoxy and 1/2 standard plate glass front on a much cheaper budget.
It is also less permenant should you wish to move it.

WhitePine · Post by **WhitePine** » 23 Oct 2006, 01:29

I agree with Larry. You can build a wood and glass tank much cheaper. Just do a search on this site for plywood tanks and do one using your favorite search engine. you will end up useing plywood, glass and fiberglass resins. you can then fill this tank with what ever you like... and finish the outside as well.

Check this link also:

http://www.plantedtank.net/forums/photo ... light=pond

Not cheap but great looking.

ali12345 · Post by **ali12345** » 23 Oct 2006, 09:37

Hi,
thanks - I haven't priced the bricks up yet but I think we will go with them. Where it will be is a connecting area between 3 buildings so has been made to match the brickwork of the original buildings so there is a lot of exposed brickwork. I think you are right about the support for the brickwork of the tank/pond. We will have a back liner of bricks but the back of the tank will be against the wall and for at least 18" on one side too. I'm hoping this will help. I really don't want to make any mistakes with this size of project - there is a stone floor so water would not be as bad a problem as in some places but some of the fish I have had for many years.
Do you think that a plywood structure with a non structural brick facing would be the way to go?
Alison

apistomaster · Post by **apistomaster** » 23 Oct 2006, 12:42

Yes, that would work. If you only use unreinforced brick and mortar, then structural failure is virtually guaranteed.
Reinforced brick walls are expensive ways to contain this amount of water. Properly waterproofed, the plywood tank can have a nonstructural facing matching the surrounding brickwork. You should not rely on the brick facing for any structural support.

MatsP · Post by **MatsP** » 23 Oct 2006, 12:57

I'm _NOT_ a structural engineer, but I have some experience in building and tearing down both wooden and brick structures (most recenty ripping out the brickwall at the front of my house), and I'll agree that an aquarium built from the right type of plywood and wood will be stronger than a brick one (partly because it's got SOME flexibility - bricks don't like to "move" even a little bit - they just crack or dislodge themselves"). Bricks are great for carrying a load on top of them, but don't like being pushed or pulled!

As an experiment: Fit a square meter of 3/4" plywood on a couple of 4x2 (2x4 for the US contingent) and use a 10lbs sledgehammer to break the ply.

Then build a brick-wall of double bricks of the same size (and leave it for a month).

I bet there will be more plywood left after 5 minutes than there will be of the brick-wall...

--
Mats

ali12345 · Post by **ali12345** » 23 Oct 2006, 16:05

Hi,
it really is surprising about brick being weaker than ply. I assume it is marine ply or something similar. Then it would be a butyl type lining inside the ply frame then?
Alison

MatsP · Post by **MatsP** » 23 Oct 2006, 16:27

You need a "water resistant ply", but I'm not sure marine is better than the "suitable for bathroom walls" type of "construction ply". The designs I've seen don't use a butyl lining [althoug that's probably possible], but a epoxy (plastic) coating on the ply itself, usually combined with a fibre-glass to reinforce it - the same construction as a plastic bath-tub for example.

The reason I'm really saying "you don't need marine ply" is that the ply isn't supposed to get in contact with the water itself (other than occassional spill/splash), so it doesn't need to be ply suitable for submersion in water. [Although for a couple of sheets, it's probably not a HUGE difference, compared to the full price of the tank]. An 8 x 3 x 3 tank will require three sheets of 8 x 4 ply [one sheet at the back, one at the bottom and little less than half a sheet on either end].

You will also need a good amount of 4 x 2 timber to hold the ply in place - that's where the REAL strength comes from. Make sure you understand how to join these together [or the person building the tank, at least does]. The idea is to avoid sheer-points where a small break will cause the whole thing to "fall apart". Some steel bracing may come in handy for corners and such. Again, it doesn't have to be "marine" quality - rusting here isn't a major problem - water should be contained by the epoxy and front glass (with suitable silicon seal around the glass of course). If that fails, no matter of water-resistance will really prevent the water from coming through - unless it's coming trhough REAL slowly...

You'll also want some high quality poly-urethane varnish for any edges of wood that is likely to get splashed/spilled on - as the wood needs to stay in shape, and varying water content is not helping on that... At all...

--
Mats

ali12345 · Post by **ali12345** » 23 Oct 2006, 16:50

Thanks - that has given me a lot to think about.
Alison

MatsP · Post by **MatsP** » 23 Oct 2006, 17:34

Here's a few good links (my personal opinion) using different techniques to build ply-tanks:
http://www.reefcentral.com/forums/showt ... did=674932
http://www.malawicichlidhomepage.com/pa ... dtank2.htm
http://www.cichlid-forum.com/articles/d ... tank_1.php
http://www.cichlid-forum.com/articles/d ... arium3.php
http://frontosa.com/articles/articlesdisplay.cfm?aid=14

These are just five of the first links I got from Google on "plywood tank".

--
Mats

apistomaster · Post by **apistomaster** » 23 Oct 2006, 17:40

Please go to http://www.GARF.org. There you wil find a section on large plywood aquarium construction. Just plug in your numbers and a complete plan, materials list and construction instructions will be generated.
You do not need additional steel or lumber reinforcing members.
Concrete and brick are strong in compression but typically 1/10 as strong in flexure. That is why rebar is added to concrete construction. The combination results in a material stronger than either of the two materials as long as the steel placement is engineered correctly. I have some expertise in this field having been in the construction materials testing and construction inspection field for over 27 years in an area where structures are designed for earthquake resistance. I am a licensed special inspector of reinforced concrete, prestressed/post-tensions concrete, reinforced masonry, and structural steel unlimited license autorized for complex structures, ie. skyscrapers, bridges and the like.

MatsP · Post by **MatsP** » 23 Oct 2006, 17:48

garf.org's calculator (http://www.garf.org/tank/buildtank.asp) is not designed for a tank that is 96" (8') long and more than 24" tall - presumably because the limits of plywood strength required re-inforcement which the calculator itself isn't capable of??

--
Mats

apistomaster · Post by **apistomaster** » 23 Oct 2006, 17:59

Then I recommend that the services of a professional be engaged. The results of catastrophic failure are unacceptable unless this tank is going to be set up on a patio. At least if a professional is hired they will have liability insurance.
PC member, whitepine, builds tanks much larger than this using other materials. I would consult with him.

snowball · Post by **snowball** » 25 Oct 2006, 01:45

fwiw, in researching materials for some furniture I intend to build, I've noticed that what is refered to these days as marine grade ply is just ply with nice end veneers that have few(er) knots. Needless to say, this costs an arm and a leg, whereas plain old structural grade ply just costs an arm.

apistomaster · Post by **apistomaster** » 25 Oct 2006, 03:46

That is why a/c grade is just fine to use. You will be infilling irregularities with 'bondo' and painting 3 coats(or more)of epoxy paint, lightly sanding each coat except the last, of course.
If you are thinking of lowering the heighth to 24 inches then there will be no special structural problems. It will also save on the cost of glass as 3/8 inch plate should suffice for a 24 in high tank.