325gal Plywood Build

A

Addicted2CAs

Member
So I figured I'd start another build blog here as this site and the people here rock!

Knowing that I already have a terrible case of MTS and am in love with big tanks (200+) I looked into the cheap way of doing them, Plywood aquariums. At first I was extremely skeptical as "Plywood" and "aquarium" in the same sentence makes no sense! With a couple months of google and lots from MFK I decided to take the plunge. This first build is "small" as my old man had a 3 sheets of 3/4" 7-ply cabinet grade plywood, 2x4's, and lots of oak laying around so the dimensions came from trying not to buy more wood. The water holding dimensions are 70.5"L 35.25"D 30"H.

To put the main plywood part together I used biscuit joints every 6 inches, regular wood glue, and stainless steel 2.5" screws every 3 inches. The point of the biscuit joints being to counteract the water weight wanting to slide the sides and back off the bottom. They provide an insane amount of shear strength when combined with the wood glue. The stainless screws are really just a paranoid feel-safe measure! Please criticise on any of this, I am more than open for suggestions. As I said this is the first and "test" ply build, there is already a 600gal in the pipeline if these methods work with this one.


The Oak front attached and drying. I used butt joints to create the oak frame and then biscuits and polyurethane wood glue to attach it to the plywood.

Two layers of fiberglass mat wet-out in the seams. It becomes very transparent and is hard to see.

Using the resin alone to waterproof and fiberglass in the seams for strength as there will be little external bracing. I also have blue pigment for the resin which will be applied in the last couple of coats for a solid look.

A random little person helping put together the 4 main stand supports. Again I butt jointed these for some immense strength.

The finished supports.

The resin kit. This bad boy cost me $220 shipped, easily the costliest part so far, well worth it! The pumps and the solid directions are extremely convenient and easy.

Partially finished stand and tank just for a nice weekend closing shot.
 
N

Nobettername

New Member
I look forward to seeing the finished product and would consider this if it ends up working well for you. Might look into a spray in/on liner( truck bed liner? ) to protect your resin. Check chemichals first.
 
A

Addicted2CAs

Member
Thats exactly why I put it here. Not everyone has the money for large tanks and I know alot of us want them! I just want to share what I learn and help out if someone else wants to do this.

As for a liner I have tossed that back and forth many times. Pond armor, rubberizit and a few others are good but quite expensive. Epoxy resin, when dried is chemically inert so I don't see that being an issue. This particular stuff is boat building resin so I just applied common sense that if it can be submerged on a boat hull in saltwater and be fine, it will surely work for this application! The only reason to coat it would be UV protection which isnt an issue here.
 
Cory

Cory

Administrator
Staff member
I'm interested to watch this unfold also. As I have a MBU puffer that would love a new custom dimensioned tank.
 
A

Addicted2CAs

Member
Thanks JimA! I did forget to mention that one important part! I am going to make a solid oak frame for the top much like the front. It will probably be 3-4" wide all the way around with a solid 5-6" brace down the middle, front to back. The plywood that will surround the stand will also come up about 4-5" from the bottom of the tank providing a bit more resistance should the walls feel the need to really bow. Between the biscuits top and bottom I dont see an issue. Another cool part about wood is that it will flex alot more than glass or acrylic before breaking.

Exactly Aquarium Co-op. Other than the fun of constructing this beast the custom dimensions are the coolest part. Whatever you think of and want for your particular fish or space needs and you can have it with a plywood at a fraction of the cost of a custom tank. I was actually thinking of a 600gal with the front and right sides being a glass viewing area, somewhat like a corner tank. oh the possibilities!
 
A

Addicted2CAs

Member
Little bit of an update. Got the glassing done. I had enough for almost 4 full layers and if that isn't strong enough I don't know what is! On each layer of glass in the seams, I cut different width strips and staggered each layer left/right to each seam, then the final strip as you can see in the pic is fairly wide at about 5". Threw 2 more regular resin coats over that and just started with the blue pigment in which I managed to get one coat done.

The fiberglass and resin really wasn't hard to work with with the right tools and some patience. It is actually quite fun! Couple more coats with the blue pigment and that part should be done. The would has stopped sucking up the resin so thats a good sign!







 
A

Addicted2CAs

Member
Finally done with the fiberglass and resin! Contrary to what I have read in other threads the fiberglass and resin was a joy to work with.....when I had all the right tools lol. Patience and the right tools is the trick and it all turned out great in the end.

So the upright seams and the bottom left and right, front to back seems all have 4 solid layers of fiberglass and the front and back, side to side seams have 4 full layers and a 2foot length in the middle of the seams. I ran out at that time and figured the middle was best as that is where the most bowing will occur. Then I added a full piece of 6oz mat from left side, down across the bottom then up the right side and a piece across the back to tie it all together. All together about 8 coats of resin in there aswell. If this thing leaks or breaks I will be highly surprised!



The blue turned out better than expected. It did not cover the wood completely which I like. Only the darkest of the wood grain is showing through.

 
A

Addicted2CAs

Member
So while the tank portion is on hold while I acquire glass I figured I would work on the sump. Being as I am not much of a pre-planner, I got a basic idea in my head and went with it. The original design had three sections: wet/dry, planted/fry grow-out area, and return area. I then realized I wanted a Peat/chemical shelf under the wet/dry as this will be a S/A tank and I need the peat room. Oh, and the tank is a 125, 4'L, 18"D, 30" tall. Yeah I love filtration!

With that in mind I got to work. The materials I used were a free 4x8 sheet of Polycarbonate for the baffles, some random PVC parts and a 5gal bucket.

The far left and right baffles will be coming up a few inches for flow. Need to reseal the bottom of the tank first.



 
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