My idea for a DIY plywood aquarium

[Big Fish Freak]

Almost ready to start building!! Just a couple more questions..
can I use birchwood? I have seen a lot of ppl just using plain old plywood, but I can get birch for $10 less than the other kind..just didnt know if it was safe to use birch or not..probably wont matter but better to be safe than sorry right?

 

[coolkeith]

Almost ready to start building!! Just a couple more questions..
can I use birchwood? I have seen a lot of ppl just using plain old plywood, but I can get birch for $10 less than the other kind..just didnt know if it was safe to use birch or not..probably wont matter but better to be safe than sorry right?

IMO, Birch Plywood is about 10x better than sanded plywood. It's just so much nicer to work with.
It's surface is smoother and harder.
It flexes less.
Holds screws better.
Has fewer core voids.
Get sharper crisper corners if you use a good saw blade. So the pieces fit and align better.
Doesn't soak up liquids like a sponge. So you get more coverage per volume with the epoxy on the 1st coat/wetting.
It's smooth surface it less harsh on cheap paint brushes. Bristles from chip brushes won't get stuck in the grain and sponge brushes will last longer.
Less raised grain after it's wetted and fewer air bubbles. So there's less sanding before the second coat.
And it has a cabinet grade finish.

 

[Big Fish Freak]

IMO, Birch Plywood is about 10x better than sanded plywood. It's just so much nicer to work with.
It's surface is smoother and harder.
It flexes less.
Holds screws better.
Has fewer core voids.
Get sharper crisper corners if you use a good saw blade. So the pieces fit and align better.
Doesn't soak up liquids like a sponge. So you get more coverage per volume with the epoxy.
It's smooth surface it less harsh on cheap paint brushes. Bristles from chip brushes won't get stuck in the grain and sponge brushes will last longer.
Less raised grain after it's wetted. So there's less sanding before the second coat.
And it has a cabinet grade finish.

Thanks Keith, sounds like I know what I'm gonna be using! I'm hoping to start building next weekend..
just gotta get supplies now..

 

[Big Fish Freak]

Also, I was curious about this...since a sheet of plywood is 8'x4' and my tank is 8'x5' I was planning on making 2 4'x5' pieces of plywood for the bottom..obviously that is not the most cost effective cut as it will force me to use 2 full sheets and I won't be able to use the scrap pieces for the tank..
Now, my question is that since I will have a sheet of plywood resting between the tank and stand (I plan on using 1/2" OSB) would it be okay to use a piece that is 1'x8' and attach it to the regular sheet of plywood to make the bottom piece?

Being that the stand is also gonna need to use 2 sheets of ply to make it 8'x5' I figured I would use 2 sheets of OSB for the 4'x5' pieces as both sheets of OSB will only cost me $10 (and I probably have some scraps to make it) and doing it this way will save me $40. With the sheet of ply under the tank and the supports under the stand I don't see any huge risks with it wanting to come apart..

I could also do 2 30"x96" pieces as well..both will result in saving the extra sheet of ply for the tank...I just want to make sure that doing it these ways won't compromise any stability or make the weak spot any more susceptible to leaks..

 

[coolkeith]

Also, I was curious about this...since a sheet of plywood is 8'x4' and my tank is 8'x5' I was planning on making 2 4'x5' pieces of plywood for the bottom..obviously that is not the most cost effective cut as it will force me to use 2 full sheets and I won't be able to use the scrap pieces for the tank..
Now, my question is that since I will have a sheet of plywood resting between the tank and stand (I plan on using 1/2" OSB) would it be okay to use a piece that is 1'x8' and attach it to the regular sheet of plywood to make the bottom piece?

Being that the stand is also gonna need to use 2 sheets of ply to make it 8'x5' I figured I would use 2 sheets of OSB for the 4'x5' pieces as both sheets of OSB will only cost me $10 (and I probably have some scraps to make it) and doing it this way will save me $40. With the sheet of ply under the tank and the supports under the stand I don't see any huge risks with it wanting to come apart..

I could also do 2 30"x96" pieces as well..both will result in saving the extra sheet of ply for the tank...I just want to make sure that doing it these ways won't compromise any stability or make the weak spot any more susceptible to leaks..

Depends on the stand. If the stand was going to be solid mass of cinder blocks you could probably do that. If there is a large gap in the blocks to make room for a sump, you'll probably need to put some kind of framework on top of the block stand so that the plywood is fully supported and screwed down into something.

I'd wouldn't go with OSB either since it's not ideal for aquatic applications. If it gets wet, it's basically destroyed. If you accidentally drop it or bang the edges, chunks of it will probably break off. It's riding on your luck and lowering all your safety factors.

 

[Big Fish Freak]

Depends on the stand. If the stand was going to be solid mass of cinder blocks you could probably do that. If there is a large gap in the blocks to make room for a sump, you'll probably need to put some kind of framework on top of the block stand so that the plywood is fully supported and screwed down into something.

I'd wouldn't go with OSB either since it's not ideal for aquatic applications. If it gets wet, it's basically destroyed. If you accidentally drop it or bang the edges, chunks of it will probably break off. It's riding on your luck and lowering all your safety factors.

I was talking OSB for the ply that the tank is going to sit on. I am doing birch ply for the tank. I could go with 2x4's to make a frame around the edges of the cinder block instead of sheets of ply. I could also just cut pieces of ply to fit on the blocks and rest the tank on that..I can line cinder blocks across that seam to make sure it's supported..
I am thinking of doing a parallel sump so that I can get a smaller return pump and save on electricity so room under won't be an issue..

 

[coolkeith]

I was talking OSB for the ply that the tank is going to sit on. I am doing birch ply for the tank. I could go with 2x4's to make a frame around the edges of the cinder block instead of sheets of ply. I could also just cut pieces of ply to fit on the blocks and rest the tank on that..I can line cinder blocks across that seam to make sure it's supported..
I am thinking of doing a parallel sump so that I can get a smaller return pump and save on electricity so room under won't be an issue..

Yeah, I know the OSB is for the stand's top. I understand the attraction to it because it's so darn cheap and could save a few dollars. Could it do the job? Certainly yes. If it gets wet and swells up, could it cause the tank to fail? Probably not. Would I use it? Nope. I have a long list of complaints about working with it. It's really not engineered to be cut into pieces. It's meant to be used in full sheets, as the edges have been treated with a waxy substance so that it will resist both chipping and moisture. Even if it's painted or sealed to prevent it from getting wet and swelling up, you still have to be extra careful with it, since the edges/corners can break off in chunks if you handle it incorrectly during transportation or assembly. When driving in screws near the edges, the edges will sometimes crack and fail. Handling large sheets of OSB isn't easy either since it flexes more and is heavier than standard plywood. The surface isn't smooth at all. So painting it or getting it completely sealed is difficult unless you have a spray gun. Then even after it's painted, it still looks like an abortion. It took a lot more work to get the final result too. End rant. You may have better luck and less frustration with it though.

 

[Big Fish Freak]

Then even after it's painted, it still looks like an abortion.

That is quite possibly the funniest thing I have ever read

What about fiberglassing it? That should solve the issues no? But then again I may as well just fiberglass the cinder block in that case..I will figure something out.

Is there a specific fiberglass mat I should use? I've never used fiberglass before so any info is good info for me.

 

[coolkeith]

That is quite possibly the funniest thing I have ever read

What about fiberglassing it? That should solve the issues no? But then again I may as well just fiberglass the cinder block in that case..I will figure something out.

Is there a specific fiberglass mat I should use? I've never used fiberglass before so any info is good info for me.

Fiberglassing OSB would be difficult since it's not a smooth surface. Expensive too. Maybe look into using 7/32" moisture resistant underlayment . It usually costs about $12 for a 8x4 sheet. It's nice and easy to work with and as smooth as can be. It's thin and won't add any structural support, but it's good to use as a surface paneling if there's something solid underneath it.

For the type of fiberglass cloth, it kind of depends what route you go. Are you fiberglassing the entire tank? The entire inside or outside or both. Or just the corners? You may need to use a few different types of cloth.
If you use a stiff fiberglass cloth on the inside corners, you sometimes get a hidden gap, that looks like this:

.
So for corners you'd want to use a more pliable cloth, than you'd use for flat surfaces.

 

[Big Fish Freak]

Fiberglassing OSB would be difficult since it's not a smooth surface. Expensive too. Maybe look into using 7/32" moisture resistant underlayment . It usually costs about $12 for a 8x4 sheet. It's nice and easy to work with and as smooth as can be. It's thin and won't add any structural support, but it's good to use as a surface paneling if there's something solid underneath it.

For the type of fiberglass cloth, it kind of depends what route you go. Are you fiberglassing the entire tank? The entire inside or outside or both. Or just the corners? You may need to use a few different types of cloth.
If you use a stiff fiberglass cloth on the inside corners, you sometimes get a hidden gap, that looks like this:
*insert pic*
So for corners you'd want to use a more pliable cloth, than you'd use for flat surfaces.

I will look into the underlayment..I am planning on just doing the corners and seams..I was thinking I would do 2 layers of a more flexible cloth and just alternate the "grain" of the cloth so it makes a sturdy seal. Do I need to let each layer of fiberglass dry before applying the new layer or do I wet the first layer and then put the second layer on after the first layer is completely wet?