Hi, first off please forgive me if this project is off-topic for MFK. I was referred here by another user on an aquaponics forum. I apologize if anyone is offended by aquaculture / raising fish for eating.
I'm in the planning stages of adding a new tank to my aquaponics system. This is freshwater, will house Black Pacu (Colossoma macropomum), and will be housed in a greenhouse environment. The space I have available is approximately 20ft x 14ft, so I am planning on a tank with inside dimensions of 12ft length x 6ft width x 5ft height (depth). This will give me enough room to work around the tank and perform maintenance etc.
The overall design/construction of the tank will ideally be a scaled-up version of the 500 gallon plywood tank I built a few months ago: The walls and floor were constructed with 2x4 studs, 3/4" plywood and liquid nails, plus ample fasteners. The edges of each wall had steel reinforcing plates with holes, and 3/8" carriage bolts were used to tie the wall corners together and to tie the walls down to the floor panel. The bolts are fantastically strong and most of the load at the bottom is shear loading on the bolts as the water is trying to blow the bottom of the walls outward. The advantage of this construction is that I can assemble everything flat on the ground, and also the tank can be disassembled and moved if necessary.
For the 2700 gallon tank, I will likely step up the construction to 2x6 custom engineered wood structural members with two layers of 1/2" exterior plywood laminated together and overlapping. I may go to 1/2" (or larger) bolts as well. I've done another project where I used strips of 3/4" wood, laminated together with a urea-formaldehyde glue (the same thing that Glu-Lam beams use). This construction produces an incredibly strong result (like, park-your-car-on-it strong). A 4x6 beam made of five layers of wood, glued up with a UF glue, will have several times more strength than a normal 4x6 framing lumber member.
I would like to include at least one large window on the side of this tank. I'd like to allow for quite a bit of a safety margin as this tank will be in more of a "work space" and I don't want to accidentally whack the window and crack or shatter it. The window will be set into a recess in the wall's framing and will be supported by a minimum of the equivalent of a 4x6 beam around it's entire perimeter. I would likely mount the window about 12 to 16 inches above the bottom of the tank so as to reduce the water pressure that the window experiences.
There are a couple waterproofing methods I've considered. First up is to use an EPDM synthetic rubber food-grade liner spread out on the inside of the tank. This would work great if there was no window to account for. The second waterproofing option would be to coat the walls and floor with fiberglass + epoxy. If I went with this option, I would like to do the fiberglassing to each individual wall panel and the floor panel, and seal the seams with silicone as I bolt the panels together.
I have a couple questions at this point.
I'm in the planning stages of adding a new tank to my aquaponics system. This is freshwater, will house Black Pacu (Colossoma macropomum), and will be housed in a greenhouse environment. The space I have available is approximately 20ft x 14ft, so I am planning on a tank with inside dimensions of 12ft length x 6ft width x 5ft height (depth). This will give me enough room to work around the tank and perform maintenance etc.
The overall design/construction of the tank will ideally be a scaled-up version of the 500 gallon plywood tank I built a few months ago: The walls and floor were constructed with 2x4 studs, 3/4" plywood and liquid nails, plus ample fasteners. The edges of each wall had steel reinforcing plates with holes, and 3/8" carriage bolts were used to tie the wall corners together and to tie the walls down to the floor panel. The bolts are fantastically strong and most of the load at the bottom is shear loading on the bolts as the water is trying to blow the bottom of the walls outward. The advantage of this construction is that I can assemble everything flat on the ground, and also the tank can be disassembled and moved if necessary.
For the 2700 gallon tank, I will likely step up the construction to 2x6 custom engineered wood structural members with two layers of 1/2" exterior plywood laminated together and overlapping. I may go to 1/2" (or larger) bolts as well. I've done another project where I used strips of 3/4" wood, laminated together with a urea-formaldehyde glue (the same thing that Glu-Lam beams use). This construction produces an incredibly strong result (like, park-your-car-on-it strong). A 4x6 beam made of five layers of wood, glued up with a UF glue, will have several times more strength than a normal 4x6 framing lumber member.
I would like to include at least one large window on the side of this tank. I'd like to allow for quite a bit of a safety margin as this tank will be in more of a "work space" and I don't want to accidentally whack the window and crack or shatter it. The window will be set into a recess in the wall's framing and will be supported by a minimum of the equivalent of a 4x6 beam around it's entire perimeter. I would likely mount the window about 12 to 16 inches above the bottom of the tank so as to reduce the water pressure that the window experiences.
There are a couple waterproofing methods I've considered. First up is to use an EPDM synthetic rubber food-grade liner spread out on the inside of the tank. This would work great if there was no window to account for. The second waterproofing option would be to coat the walls and floor with fiberglass + epoxy. If I went with this option, I would like to do the fiberglassing to each individual wall panel and the floor panel, and seal the seams with silicone as I bolt the panels together.
I have a couple questions at this point.
- If I were to use an EPDM pond liner as a waterproofing method, is it possible to seal the window to the EPDM rubber liner?
- How much water pressure can a silicone seam handle, assuming the joints are really tight and well supported?
- I'm leaning towards glass as a window material, as I think it would cost less and I'm not concerned about weight or anything. Should I consider a different material?
- If glass is good, then tempered, or not?
- How thick of window material do I need?
- Should I fit a bulkhead fitting in the floor of the tank to provide a way to drain the tank completely?
