Large Plywood Tank

T

tomason

New member
I'd like to build a 96"x24.5"x32" tank out of plywood, and I've been trying to find answers to the following questions all over the internet, but I just haven't had any luck yet:

1. I've found 2 documented cases of >400 gallons tanks being build using the GARF plans, however GARF's site recommends not building a tank longer than 48" when the height is more than 24". Both of those guys did it anyway and it held water long enough for them to get them all set up and stocked and take pictures of it. Is that a smart thing to do long-term?

2. The GARF plans call for a very large (12") plywood brace across the top. A tank 8' long would probably need 3 or so of them. That would really screw up the reef lighting! Could those braces be made of acrylic instead? Could they just be screwed on like the plywood ones?

3. If I can't use acrylic for the braces, could I compensate by making the hood hold it together? Or how about a frame around the top made of 2x4's?

4. Should I just bite the bullet and make it out of acrylic for a lot more? That's what I was originally planning before I realized there's only going to be 1 viewable side where my wife wants to put it.

Thank you!

-Tom
 
I would think that if you did a 3 " lip out of plywood you could cement a couple of strips of acrylic under the lip w/ weldon 40
 
So would weldon 40 really bond with the epoxy-painted plywood?

Or what about DOW 795 silicone as the bonding agent plus screws through the plywood lip into the acrylic brace?

What thickness of acrylic should I use?

Thank you!

-Tom
 
Wow! That was a cool article!

Another question: Would there be any problem with finishing the outside of the tank the same as the hood and canopy? I don't see why not, since the epoxy paint keeps the plywood dry anyway. I just thought I'd ask just in case.

-Tom
 
It's been a few more days now, and I've found a lot more information out there. Plywood tanks seem to be extremely popular with the cichlid crowd!

I'll post the most common methods for sealing the plywood in case any of you might have some insight into them:

1. Coat the interior plywood surfaces with 2-part epoxy paint and put a bead of silicone along all the inside edges

2. Coat the inside with just epoxy resin

3. Go all out and fiberglass the inside and then apply a couple coats of 2-part of epoxy paint to finish it

4. Just put fiberglass tape along the inside edges and seal the rest of the wood with just the epoxy resin

#1 scares me, but people have done it successfully.

#2 is better.

#3 is definitely over-kill and puts the cost of the tank up past acrylic.

#4 seems like a good balance of strength reinforcement for the seams, and the epoxy resin is definitely waterproof. After all, that's what boat-makers use for the hulls.

The plywood is extremely strong - stronger than glass and acrylic. It provides all the necessary structural support. The sealant just has provide a water barrier and not crack if flexed too much and then leak. That's where the fiberglass along the inside edges comes in. It greatly increases the tensile strength of the waterproofing where it needs it.

I was hoping to be able to afford a Starphire glass panel because I would be saving so much on the rest of the tank, but alas it's WAY more expensive than I could have imagined. The cost of the glass using regular 1/2" tempered plate glass is $262. The Starphire glass is $727!!!!!!!! That's more than all of the acrylic would be to make the whole thing!

There's so much information among the reef websites about acrylic tank construction, and even some on glass tank construction. However, there's hardly anything on plywood tanks. I think that's interesting. Perhaps it has something to do with the tank cost being so much less (relatively speaking) for a reef system than it is for the freshwater folks. Who knows!

-Tom
 
Re: Large Plywood Tank

tomason said:
I'd like to build a 96"x24.5"x32" tank out of plywood, and I've been trying to find answers to the following questions all over the internet, but I just haven't had any luck yet:

2. The GARF plans call for a very large (12") plywood brace across the top. A tank 8' long would probably need 3 or so of them. That would really screw up the reef lighting! Could those braces be made of acrylic instead? Could they just be screwed on like the plywood ones?

3. If I can't use acrylic for the braces, could I compensate by making the hood hold it together? Or how about a frame around the top made of 2x4's?
Click to expand...

Here's a thread in which someone used threaded rod for bracing. It will not interfere with your lighting.
 
Re: Large Plywood Tank

tomason said:
I'd like to build a 96"x24.5"x32" tank out of plywood, and I've been trying to find answers to the following questions all over the internet, but I just haven't had any luck yet:

1. I've found 2 documented cases of >400 gallons tanks being build using the GARF plans, however GARF's site recommends not building a tank longer than 48" when the height is more than 24". Both of those guys did it anyway and it held water long enough for them to get them all set up and stocked and take pictures of it. Is that a smart thing to do long-term?

2. The GARF plans call for a very large (12") plywood brace across the top. A tank 8' long would probably need 3 or so of them. That would really screw up the reef lighting! Could those braces be made of acrylic instead? Could they just be screwed on like the plywood ones?

3. If I can't use acrylic for the braces, could I compensate by making the hood hold it together? Or how about a frame around the top made of 2x4's?

4. Should I just bite the bullet and make it out of acrylic for a lot more? That's what I was originally planning before I realized there's only going to be 1 viewable side where my wife wants to put it.

Thank you!

-Tom
Click to expand...

I really am tired of GARF's misinformation...

1.) I have seen a freshwater tank with the dimensions of 96" x 48" x 48". The guy underbuilt the tank. It was pretty scary, but held water. If you are really concerned, just laminate two sheets of plywood together.

2.) Not nescessay. Look at David Grigor's web page. Also look at the thread that gev posted. It has pics of David's tank starting at page two. He used a very small Euro brace along with threaded rods. You could even use just the rods.

3.) You could do that, but see #2 again. I would recommend the rods.

4.) I think it is more fun to do as you are doing it. Unfortunately, I never finished the wooden tank I was going to build. I have since re-designed and am planning on making it bigger... A LOT bigger. Wood is much more forgiving than acrylic and easier to work with, not to mention cheaper.

Mark
 
Re: Re: Large Plywood Tank

Re: Re: Large Plywood Tank

MarkS said:
I really am tired of GARF's misinformation...

1.) I have seen a freshwater tank with the dimensions of 96" x 48" x 48". The guy underbuilt the tank. It was pretty scary, but held water. If you are really concerned, just laminate two sheets of plywood together.
Click to expand...

How is a recommendation misinformation?

When I designed the calculator I was assuming people with common sense would be using it. There were people that built the tank like the one you mentioned and ended up with a livingroom full of water. We decided to temporarily place limits on the size of tank the calculator will design until I had time to fix it. Since I am no longer volunteer at GARF, it will probably stay the way it is...

Thanks

Scott
 
I don't think there is anything wrong with the GARF plans. If I was going to go bigger I would just modify them for the extra size. Isn't that what DIY is all about...get a good idea from someone or something else and make it your own?

The threaded rods make a lot of sense.
 
Common sense has nothing to do with it. Plywood is very strong and if constructed right, there is no reason why someone could not go taller than 24" if they wanted too. I am planning a 96" long x 96" deep x 48" tall aquarium out of plywood. It would only have one viewing panel and would be made for a future in wall tank. All sides, including the bottom, would be double laminated out of 3/4" plywood. Epoxy would be used to laminte the wood. The front glass would be 1" thick. For the front, there would be two 1/2" pieces sanwiched between two 3/4" pieces. The 1/2" pieces would be inset about 2" so the glass seats down between the 3/4" pieces. I am very comfortable with this design and have no fear of it leaking.

I recommend that he gules the edges with Professional Strength Liquid Nails. Use 4" screws every 4". I'd definitely go with David's method of using threaded rods. It would probably be best to use 4 or five.
 
Hey, thanks for the info! I hadn't seen that one gev posted before.

GARFVolunteer, that's also information I was looking for!!! I mentioned in my first post that the tanks lasted long enough to post them on the internet, but I didn't know if they were still working. :)

So it seems that as long as the wooden structure is sound, epoxy paint is just fine. I've been spending most of my time researching ways to seal it, when I guess I should have been researching the rigidity of the wooden structure to prevent the flexing and bowing which cracks the epoxy paint.

Mark, I noticed that you used epoxy resin. That's what I was planning on. It's cheaper than the 2-part epoxy paint. You also mentioned that you only used 2 cups to do the bottom and sides. Do you think 1 gallon would be enough for me to do the inside and outside back of the tank?

Epoxy resin doesn't have nearly the fumes of the epoxy paint either. Plus it'd work better for the fiberglass taping in the corners. David used fiberglass with epoxy paint, which isn't designed for composite work.

I don't think it'd be necessary to double-up the plywood for my case. Lots of screws, liquid nails, and adequate top bracing should be fine.

Thanks again!

-Tom
 
MarkS

Common sense has everything to do with it when you are designing a calcualtor for others to use. Your plans make sense but the way the calculator was before I put the limits on it, someone out there would have tried building one like it with 3/4 inch plywood. We decided to error on the low side with the linits. The wording could have been better and said something about "The calculator is limited to...."

Eventually the calculator would have evolved to handle larger tanks as time allowed me to work on it. However it is a mute point now.

Thanks,

Scott
 
You are right and I apologize. I would delete what I wrote, but it's well past the 1 hour limit...
 
My friend and I built a plywood tank 10 feet long, and 24 by 24 - with a thin wood brace I think 1 3/4 " wide every 2 feet.

This was in about 1970, in his parents house. We moved on in life, but the tank stayed behind. In the 80s it was moved to a Chinese restaurant, owned by a friend of his - still going strong over 30 years later.

But don't skimp on the bracing - anything that will prevent movement will do - rods, acrlyic, anything - I thought I could get away with a 4 foot span on another tank. WRONG. I described the disaster in another thread. But a brace every 2 feet seems to work. And don't skimp on the glass quality!

That price for Starphire seems way too high. Maybe you can get it cheaper somewhere else.
 
Thanks, JohnM99. I was planning on putting a 3" rim of plywood all around the top (just like the face - 1 sheet routed out) and then 1 brace every 2 feet, so 3 braces total.

I'm going to use a sheet of tempered 1/2" glass, so that should be fine too. The price I was quoted for Starphire glass above was for TEMPERED 1/2", if that makes a difference. 1/2" though doesn't seem thick enough to be a big deal from pictures I've seen. I know it's been discussed before around here so I'll do some searches, but if any one has comments to make on that I wouldn't mind! ;)

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

That Devoe 233H Bar-Rust paint is looking mighty tempting.....Maybe I won't bother with the fiberglassing ???

Thanks, everyone!

-Tom
 
Someone on saltwaterfish.com has a 1700+ gallon shark tank he built with plywood(1 viewing window). The thing is huge and absolutely beautiful. Been running for about a year now. Do a search on SWF.com for user "novice150" and you will get his posts/website detailing the construction(alot of pics too).
 
Here is the link to my horrible memory
http://reefcentral.com/forums/showthread.php?s=&threadid=242232

After I put an angle iron brace on the tank, and coated it with fibreglass, the tank was fine. With a new pane of slightly thicker glass. My brother has it - still working.

We put fibreglass tape on all the seams and painted with some special fiberglass type paint (can't remember)

With the starphire, maybe the tempering is the reason for the high price ? I am getting my 90 flat back hex made from starphire (front and sides) and it is pretty reasonable.

Good luck. I had over 10 plywood tanks at one point - very affordable, and durable.
 
Yikes! So it was the glass that gave way?

swilbs83, jayo's post up at the top was for a 1700 gallon shark tank. I've seen that article at at least 3 sites, so maybe that's what you're referring to? It is awesome!
 
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