Plywood Aquarium

[Tony2099]

 Are plywood aquarium safe? I know some who going to make 1. I dont know much about them.

 

 

[Wills]

They are safe but IMO incredibly risky, the basic aim is to make a box solid enough to line with the pond liner paint. There are a lot of good tutorials and youtube videos about this subject out there. Does your friend or yourself have any experience with building or making things?
 
One of the biggest issues I have seen with them is the lining causing problems and leaking which weakens the plywood and can render the whole tank useless.
 
How big is the intended tank?
 
Wills

 

[Tony2099]

 My brother in law going to try to make like 300 gallons or bigger. I never made a tank with wood in my life. He want to make it a monster fish tank.

 

 

[Phillysailor]

I'm building a boat, and when my son asked for a fish tank, I had no problem applying my newfound skill set to a plywood tank.
 
A veritable bible among boat builders is the Gougeon's brothers book on boatbuilding (the link is the whole book, btw... its free!) which describes all their testing and knowledge of plywood and wood construction using epoxy. The combination of epoxy, fillers and fiberglass cloth with wood and epoxy has been studied pretty exhaustively by them, and I've little hesitation to proceed while using their techniques. 
 
I've invested in an epoxy cart, with mixing tools, fillers and sandwich bags, rolls of fiberglass tape and such. I've figured out how to keep epoxy at a good working temperature, and have a heat gun at the ready when mixing and applying. I've got gloves, masks and plastic sheeting to keep  work surfaces clean, and good ventilation. I've acetone and vinegar ready for prep and cleaning.
 
I used shop grade plywood, Kreg pocket screw system, and routed out a 3/4 inch overlap 1/8" deep for the glass silhouette.  I coated the box (inside and out) two times with neat epoxy all applied before the previous layer cured. The top edges received more. I filleted the corners and taped the inside corners. I over-size drilled the bulkhead, filled the hole with epoxy, and then drilled the epoxy blank with the final hole. I sanded it all down, and applied another coat of neat epoxy. Lightly sanded and then sprayed Krylon... two separate sessions with several coats. 
 
My tank is 28"wide, 20" deep and 22" high. About 63 gal. I did not brace it, because the dimensions are within the strength I've estimated it will require. The fiberglass taping not only ensures watertight plywood edges (most vulnerable) but a smooth transition from one wall to its neighbor transfers loads the same way an arch creates architectural integrity. It tends to minimize stress risers and spreads loads throughout the structure. Plus, the Kreg system itself creates joint strength which exceeds that of the wood itself. 
 
The plywood build makes sense for me, since I am placing my tank in a built-in hutch for an old-style tube TV, and it is only viewable from the front. I'm using 3/8" glass, which has a substantial safety factor. 
 
Leak test starts this weekend, after the silicone cures!

 

[Phillysailor]

I should mention that I will brace the front of the aquarium with a face panel, and the bottom will have lighting diffuser placed to protect the bottom from scratches and dings from any heavy objects moving around. That's really the danger with this type of construction, I suppose: any defect in the epoxy layer will cause failure through water entry into the plywood. Perhaps one would sleep better at night with a layer of fiberglass laid on all interior surfaces. I'm going to proceed as contracted, tho!
 
After thinking about forces, I will put a single brace across the middle (front to back) of the tank to support the glass seat at the top. Any outward bowing could lead to leaks.