Plywood Specifications Debate?

[Potato Patatto]

Has there been any unanimous decision on the plywood needed for aquarium builds?

I’ve seen several use 3/4 birch with two layers, others swear you need marine plywood, then others swear marine plywood is the worst choice. It’s my understanding it doesn’t matter if the wood has chemicals as it’s being covered in epoxy/resin.

Am I correct marine plywood is not pressure treated? Which subjects it to the potential of rot/mold? But it is undeniably stronger due to having no voids?

I also find myself conflicted on the bracing with 2x4, I can’t help but feel building the plywood box first ensures the best “seam” due to be able to glue and screw from the outside. And when we talk about a liquid box, I think the seam is most important before the brace. The question, could you then “drop” the box/aquarium into a pre-made brace or build a brace around the built box? I’ve seen a few use the birch 3/4 and layer it with 2 sheets as the support itself free of 2x4s. Would that type of support with installing top braces be enough for 8x4x3?

Basically if you saw Joey of DIY first aquarium build versus the build of the recent Oscar tank. What would be your preference? Seam or support.. if I’m making sense.

 

[Revan]

I have a 650g plywood tank made with 1 layer of 3/4" ACX and 2x4 ribbing every 18". The vendor did not specify what species of tree the veneer of the plywood was made of. Probably fir or birch. It's been going well for over a year now, though admittedly that's not a very long time.

My understanding is that Marine-grade plywood is not typically treated. The "marine grade" comes from the core being solid with no voids. This prevents moisture from collecting inside the plywood and causing delamination. Here's a good link for information on different types of plywood.

BCX and CCX ⋆ ? ThePlywood.com

The average lumberyard or home improvement center today carries a plethora of different types of plywood, giving you a wide selection to choose from. Businesses which specialize in providing architectural trim for cabinetmakers and contractors will have even more choices, especially if you’re...

theplywood.com

I don't know if marine-grade is better to use plywood tanks, but I can tell you that mine doesn't have it and has been OK so far. I would suspect it's not a necessary factor, since our tanks get waterproofed anyway.

 

[Potato Patatto]

I have a 650g plywood tank made with 1 layer of 3/4" ACX and 2x4 ribbing every 18". The vendor did not specify what species of tree the veneer of the plywood was made of. Probably fir or birch. It's been going well for over a year now, though admittedly that's not a very long time.

My understanding is that Marine-grade plywood is not typically treated. The "marine grade" comes from the core being solid with no voids. This prevents moisture from collecting inside the plywood and causing delamination. Here's a good link for information on different types of plywood.

BCX and CCX ⋆ ? ThePlywood.com

The average lumberyard or home improvement center today carries a plethora of different types of plywood, giving you a wide selection to choose from. Businesses which specialize in providing architectural trim for cabinetmakers and contractors will have even more choices, especially if you’re...

theplywood.com

I don't know if marine-grade is better to use plywood tanks, but I can tell you that mine doesn't have it and has been OK so far. I would suspect it's not a necessary factor, since our tanks get waterproofed anyway.

Do you have a photo of yours with the ribbing? Yes that was my understanding of Marine as well, it’s the strongest due to having no voids and potentially having a blowout. Although I imagine any ribbing or studs greatly reduces that possibility so maybe it’s just a moot point all things considered. I guess anything under 1 solid sheet of plywood makes a build exponentially easier and less risky than joining pieces beyond an 8ft length of 4ft width.

 

[Dovii kid]

Do you have a photo of yours with the ribbing? Yes that was my understanding of Marine as well, it’s the strongest due to having no voids and potentially having a blowout. Although I imagine any ribbing or studs greatly reduces that possibility so maybe it’s just a moot point all things considered. I guess anything under 1 solid sheet of plywood makes a build exponentially easier and less risky than joining pieces beyond an 8ft length of 4ft width.

For plywood I utilized AC grade plywood for subfloor which has less voids I'm told. That said don't feel it makes much difference. Especially if you decide to glass the entire thing. I utilized dbm 1708 for the corners and 10oz cloth over the entire structure with epoxy resin. Afterwards top coated with 3 layers of epoxy paint, interseal 670hs.

I built a 10x4 and do agree, certainly at times I wish I had utilized measurements based on typical dimensional lumber. That said feel confident in the way I built mine. For the seams I doubled up on the studs underneath. Therefore the end of each plywood was secured to its own 2x6. Also put a double layer of DBM1708 and epoxy over every seam.

 

[Dovii kid]

Not sure if it helps but a few of mine in current state. Had a tiny leak around front panel after first fill due to not letting silicone cure long enough. So had to reinstall the panel. Lesson learned, hands down worst process I've done on any project was removing that panel.