Large Plywood Tank

tomason said:
I'd also be interested in reading your "disaster thread." :) There were a couple other scary ones I read, but this one takes the cake so far: http://www.dudeiknow.com/aquarium
Click to expand...

Yea that link definately shows how important the sealing coat is:eek2: .

I noticed that this guy said:

"Today I purchase 3 sheets of plywood. I know that my original plans called for AC grade plywood, but I decided to go with CD grade. Aside from a few "cosmetic" flaws, the plys seem to be better filled in the CD grade. Remember AC grade is more of an INDOOR wood, CD is more of an exterior wood. I HOPE this decision does not come back to haunt me later on."

I will hopefully be building a large plywood tank during the next year, I will be using birch or other cabinet grade plywood. No sense in skimping at this stage IMO.
Steve
 
I just recently bought 3/4 birch plywood from Menards and it now has 9 plys which would be good. I do not know if this is at all the stores I looked on the plywood to see where it was made and did not say anything but 18 mm so I think that it came from Canada. I would look for cabinet grade since it would not have any voids and should have more plys.
 
I used 3/4 birch plywood. solid as a rock. also used two part epoxy with a bead of silicone in the edges. dont have a leak, but I do have some salt creep along one seam......some things I read when building it recommended waterproof glue in between all the plywood joints....the way I figured it, water shouldn't make it beyond the epoxy and silicone so I passed on that....maybe I shouldn't have. may be just the excuse I need to build another bigger one.
 
javatech, that tank is really cool! It was one of the tanks I looked at before. Nice work!

Tommyc, that salt creep sounds really scary! Maybe you oughtta accellerate your the schedule for your "bigger one" so it's ready before that seam gives way. :)

So here's my current plan based on all the information I've found and received here:

- Use exterior AC grad 3/4" plywood for all the sides.

- The front and top will both be single sheets routed out to a 3" rim.

- For additional top bracing, I'll attach steel brackets to the plywood top on the front and back to thread the rod through. That way I don't have a rod and nut sticking out the front, interfering with finishing the outside of the tank. Those rods will be placed every 2 feet for a total of 3.

- To seal the plywood, I'm going to use a couple coats of epoxy resin to prep the surface, and then lay 2 layers of 6" fiberglass tape along all the inside seams. That will be followed by another 2 or so coats of resin with some black or blue pigment (I haven't decided on the color yet). The outside of the back and part of the bottom will also be sealed, because that's where all the bulkheads will be.

- The window will be 1/2" tempered plate glass attached with silicone, of course.

I feel pretty confident that that'll hold water long-term without problem.

Any last words????

I appreciate all the help!

-Tom
 
- To seal the plywood, I'm going to use a couple coats of epoxy resin to prep the surface, and then lay 2 layers of 6" fiberglass tape along all the inside seams.
Click to expand...

I was looking into building a plywood tank and all the reading and talking to people most said that they would not put the fiberglass tape in the seams. They all seemed to think that it did not add that much strength and it was a PITA to get in so it was not sticking up all over and was not easy to seal over.
 
marm64,

That's interesting. I've heard that too, but I've also heard people say it adds lots of strength. Those who fiberglassed the whole thing said they wish they had just done the corners. Many people have had success without fiberglass, so maybe I won't bother!

Thanks!
Tom
 
If you fiberglass the whole thing that might be different but if you just do the corners I do not think that it would make any differance. This is like the people that think that they should use exterior grade plywood just be safe for a leak. If it leaks the exterior grade plywood is not going to make any differance. If done correctly I do not think that the fiberglass is just going to take more time than it is worth to do. But i guess if it makes you feel more safe I would do it for that reason alone.
 
That's a good point, marm64. I really don't know much about working with composites. Epoxy paint is sounding better and better!

That Devoe Bar-Rust 233H stuff they used in the thread referenced at the beginning can even cure at temps down to 20 degrees. As we head into winter, that's a really good thing! Epoxy resin and other epoxy paints require warmer temps which I can't give them very easily.

Does anyone who knows more about fiberglass want to put in a plug for it?

Thanks again!
-Tom
 
Here is my 700g plywood tank with rubber pond liner and acrylic front. It going through a shakedown. No leaks. I should be finished in about a month.
 

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I didn't use the fiberglass anywhere on mine and only one viewing area (front pane). But I do have one bit of additional advice......after my tank cycled I was fighting a significant hair algae problem. In the course of solving the prob I added a small urchin. Don't think he solved the hair algae problem, but it's all gone now. Point is....as the walls of my tank became covered with coralline, he chewed through the coralline, through the epoxy and into the wood. Not good. Just a word to the wise. Was able to fix the prob and the tank's still running great....but it was an annoying lesson.

tom
 
TommyC
Did you consider lining the tank with 1/4" (or 1/8") acrylic after doing all of the sealing etc? I am considering a plywood/glass tank and am thinking of doing this although I had not though of the problem you encountered. Makes me more inclinded to do it now.
Alan
 
Mastino - That's a cool tank! Was the pond liner all you used to seal the plywood? Did you just use silicone to seal the acrylic viewing pane?

TommyC - How did you fix that?

Are there any other creatures like urchins which can chew through the expoxy? I've heard of plecostamus doing it in freshwater tanks. Will falling rocks crack or chip it? I'm just wondering how likely this is...

Thanks!
-Tom
 
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