Plywood Tank Build Question

[TexasMFK31]

Hey all, I am just curious as I am thinking/designing a new tank build. Is there a reason you couldn't build around a sheet of plywood to have a true 8x4 inner dimension? If you did it from 1" thick plywood, I think this would more than work. Is there a reason it would not and makes it inferior to building on top of the bottom?

 

[Lepisosteus]

I asked this same question to an engineer years ago and the numbers he came across suggest it’s stronger to do it that way. If you look at Red Sea reefer aquariums, the front and back are on the outside of the bottom. I built a 300 glass with the exact same concept and it worked great. It’s still going today at 10 years. In my opinion it’s fine to do so.

 

[TexasMFK31]

I asked this same question to an engineer years ago and the numbers he came across suggest it’s stronger to do it that way. If you look at Red Sea reefer aquariums, the front and back are on the outside of the bottom. I built a 300 glass with the exact same concept and it worked great. It’s still going today at 10 years. In my opinion it’s fine to do so.

Awesome, then I will be on it! On my upgrade, I decided against the seam bottom so I am going to do a 8x5 sheet of plywood for the bottom so I have a true inside dimensions. Then I will use a full sheet up top and cut out holes for lids. Great news!

 

[Oughtsix]

Where the sides of the tank attach to the bottom of the tank is where the highest water pressure will be. The water will be pushing down on the bottom of the tank which will be counteracted by the support from the stand. The water pressure will also be pushing the sides of the tank out.

With the sides on top of the bottom and screwed up through the bottom the screws will have a shear force that will be supported by the the plywood sides.

With the sides on the side of the bottom the force will be lined up with the length of the screws... which is not nearly as strong, especially in plywood.

I am not saying your plan won't work or even that it is a bad idea... just make sure to secure the sides to the bottom well. A 2" x 2" stick of wood around the inside bottom of the tank that you can screw into from both the sides and the bottom is one way you could reinforce this joint. The strength of the tank will depend on the design of the tank as a whole.

How tall will the tank sides be?

 

[TexasMFK31]

Where the sides of the tank attach to the bottom of the tank is where the highest water pressure will be. The water will be pushing down on the bottom of the tank which will be counteracted by the support from the stand. The water pressure will also be pushing the sides of the tank out.

With the sides on top of the bottom and screwed up through the bottom the screws will have a shear force that will be supported by the the plywood sides.

With the sides on the side of the bottom the force will be lined up with the length of the screws... which is not nearly as strong, especially in plywood.

I am not saying your plan won't work or even that it is a bad idea... just make sure to secure the sides to the bottom well. A 2" x 2" stick of wood around the inside bottom of the tank that you can screw into from both the sides and the bottom is one way you could reinforce this joint. The strength of the tank will depend on the design of the tank as a whole.

How tall will the tank sides be?

Looking to do 32" water level. I believe I am going to do the sides and then run plywood underneath perpendicular to the main bottom piece covering the sides. So it would be fixed side to the base, and bottom to just a non-water piece of plywood. If that makes since. Essentially I want that 5x8 interior dimensions without making a seam on the bottom.