PLYWOOD AQUARIUM - BEST PRACTICES

[marine_hawaii]

First a quick shout out to everyone who has put their wood aquarium plans & pics for all to see. I think this a fantastic community, and I hope we can continue to help each other to build better and bigger tanks!


That being said, there is a huge difference between a 600 gal tank and a 50,000 gal tank. Since a 600 gal seems to be more approachable for most, I'd like to focus on that size (range), and the use of plywood/wood for construction.

A great suggestion (I think it was Gator) was to use Google's free SketchUp program. I started my 10x3x4 aquarium plans on graph paper, and it was going smoothly. But I was BLOWN AWAY by using SketchUp. Being able to see the structure in 3D as you draw it is priceless. If you are a DIY person, then SketchUp is something you can not live without.

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So using SketchUp, here is the "rough draft" of the tank I'm looking to build.

A couple of ideas: I've used the basic 2x4 wall construction to create a very strong frame by using inexpensive (ish) materials. The plywood is 3/4" exterior grade stuff, the lumber is mostly 2x4 with a couple 2x6. The glass was divided into 2 sheets, 42x48 inches each, to cut down on cost.

The only "high" end item is the interior plywood, which I'm thinking will be 3/8" furniture grade (no filling required!).

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The other main point is to be able to build this whole project with a circular saw and a couple NEW blades (about $7 a pop, but sharp is key to smooth cuts). I'll use a straight edge and 2 quick clamps to run my circ saw along for (hopefully) perfect cuts.

It's a lot of wood, but it's all cheap wood. I haven't done the math on it, but he strength of the structure should be able to support 10 times the weight of the water, etc. Should hold up pretty well to earthquakes too (well, mild ones anyway).

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So here are the screen shots of the design:



A shot of the corner support. Note in the right front of this pic the 2x4 supports the 3/4" ply on both axis.




Shows the back left corner detail. The 2x4's are positioned to support every junction of the 3/4" plywood. The "furniture grade 3/8" ply is glued to the 3/4" ply.



A view of the back showing different transparencies. All the 2x4's are 12" on center. It may be overkill to not go with 14" or 16" on center, but is only a bit more wood (cheap 2x4's) giving a lot more rigidity.



Same section as above, shown looking down.



Shot looking thru the front "2x4 ply sandwich" to the under-tank supports.



These 2x4 vertical supports are 14" on center. The top is a 2x6. The sides are 3/4" plywood.



Shows the bottom "support structure" for the weight of the water. Each rib is 3/4" plywood with 2x4 running around the outside edge. All 2x4 are "screwed and glued" (2" wood decking screws, waterproof glue). These ribs are placed 12" on center.



Shows the 2x4 structure of the side walls. The 2x4's are sandwiched between two 3/4" plywood sheets running bottom to top (for rigidity and strength).



This top view shows the interior. The blue (non-translucent) is "furniture grade" plywood (3/8"). The translucent fronts are 2 glass panes, 42x48 each.




Front right. The idea of using two planes of glass came from several sources (including this forum). The Waikiki aquarium has a few tanks setup that way too. But mostly it was the size, weight, expense and structural requirements that nixed the single glass pane idea.



The front of the 10' tank. Depth is 42". Internal width is 29" (approx). Depth and width could be scaled out until the plywood shown on the far left reached 48" in width (it is 37.5" in this design).

 

[marine_hawaii]

A section view (cut away of the side).

 

[JOEG.]

nice!!

 

[Bassinkorea]

When do you plan to start this build?? it gunna look great!!

 

[Issack]

sure is a lot of bracing for a 600. that thing could survive being thrown off a cliff.. lol. Looks good though.

 

[cvermeulen]

You could get away with a LOT less beef in that tank. It doesn't have to be built like a bunker, and actually having closed walls like that provides a place for humidity, mold, insects, and rot to do their worst. Have a look at my 600 build - 3/4 plywood screwed and fiberglassed at the seams with no external bracing. The tank does not bow, bulge or wobble.

 

[marine_hawaii]

As the plywood for the wall structure is outside grade plywood, I'm not too worried about mold. Mold is a problem in Hawaii that I've dealt with before, and it is easily deterred by not using materials that mold likes to feed on. I suppose I could paint the plywood or even cut ventilation holes, but I don't see mold becoming an issue.

But I agree that in a cold climate, a reef tank room has condensation and potential mold issues that should be addressed. Since insulation (to keep the tank warm) is also a big factor, maybe using polyurethane foam in the "wall" cavities would be a good idea. That idea would also point toward the heavier plywood as that foam expands with significant pressure.

Also, the light I'm using is natural sunlight, which in Hawaii is "tropical" strong. The light will come in thru 3 skylight tubes. It's pretty effective as a mold-deterrent.

Some reasons the tank is built like a "bunker":

- The plan calls for 2 surge tanks (35-50 gallon) releasing into the display tank. The actual water level will be 6-8" below the top of the tank (rising when the surge enters). Given the rare simultaneous surge, that's roughly 800 lbs of water entering the tank in a short period.

- We have earthquakes from time to time here.

- I MUCH rather spend an extra couple hundred $$ on heavier plywood than the thousands it would cost to replace the hard wood flooring in the adjacent room. Not to mention the cost etc of rebuilding the tank if it sprung a leak (or worse). It reminds me of the tests they did with those containers they use to ship spent uranium. Are those containers overbuilt? Probably so. But the cost of failure was so high that it justified the extra cost of hardening.

- The design can be easily modified for thinner plywood (eg 1/2" versus the 3/4" I used in my design). The 2x4's could be spaced wider apart (eg 16" on center versus 12" on center).

- This is a free standing tank. It receives no support from walls etc. The weak point is the open top and the glass front panels. The plywood & 2x4 are to keep those weak points from coming apart due to the water pressure.

- The 12" spacing on the 2x4's is to keep the plywood from (ever) moving under the weight of the water. The design is to use epoxy paint (not fiberglass) and thus if the plywood moved even slightly, it could cause a leak.

- Glass aquariums are mostly held together by silicon sealant. They preform well because the glass is very rigid. So the design I used focused on the same rigidity.

There are other tank projects detailed on this site which use considerably heavier construction methods. I took my design from standard 2x4 construction practices. I think a balance needs to be found between cost and sufficiently-rigid construction.

 

[cvermeulen]

OK well you seem pretty set on your design. Making it too heavy won't hurt anything I guess, but even given all of your reasoning, you've gone hella overkill on the overall structure. If extra bracing gives you peace of mind I say go for it, it's just not necessary, in case anyone else is planning a tank and thinking this is the level of construction what's needed.

 

[JaxsBr]

So its a one piece,tank and stand combined?

Your gonna need a chair or something for maintenace,that is quite high.

 

[cvermeulen]

On other thing you might want to consider is how you're going to do maintenance on a tank that tall. Tall tanks look great, and on this premise I built my first plywood tank at 24" wide, and 36" tall. Let me tell you any time I have to retrieve something off the bottom I curse myself for not going 24" tall and 36" wide instead. Yours will be even more difficult at 42" Picture yourself on a ladder leaning over the edge of the tank with head and shoulders below the top of the tank trying to reach something. Just another thing to be aware of.