Plywood tank Question

[marinelife]

Yeah it will be heavy but with several guys and some wheels I hope we can get it!!!
Building outside and bringing it in is my only option as this is going in the location of my current tank and the living room.
The corner bracing will only be on the inside at this point but I may add some to the outside later.

 

[geraldwhite]

From what you said it sounds like your going to try and build this outside and bring it in? I just dont think you will be able to do that. 1 sheet of 3/4 weighs in at about 70LBS you have 14.. Even if you dont use them all YIKES. Thats not even talking about your 1.5" thick acrylic window..Or your 2x4 braces or the Epoxy or the fiberglass lol.. I"m up to about 1400LBS in my head....

I don't know if he has a choice here. He needs to do the Epoxy outside and the best method is pouring it from what I have seen, so that means he is going to have to stand this beast on its side.

It can be painted on but it looks really bad.

 

[marinelife]

geraldwhite: you are 100% correct and that is just another reason for the outside build.

 

[8BALL_99]

I dont know alot of the Big tank builds I've seen they build them on sight due to the size..Most big tanks are 36"+ wide so they just wont fit through a single door.. Heck even large glass tanks are built on sight alot of times.. Not saying you can't move it in. Just yikes with woood floors and all that weight + just the shear size of this thing it will be a job!

 

[marinelife]

I measured the door opening and went a little smaller on the tank. It will fit in the door and I can add a few things to the outside once it is in. If I had a large opening door I would have went larger. Also the wood floor is missing in the place the tank will go, My current tank is sitting on cement and that also is another reason for the size I picked. It had to fit in that spot and be able to get in the door.

 

[geraldwhite]

<a href=showthread.php?s=&postid=12780735#post12780735 target=_blank>Originally posted</a> by marinelife
I measured the door opening and went a little smaller on the tank. It will fit in the door and I can add a few things to the outside once it is in. If I had a large opening door I would have went larger. Also the wood floor is missing in the place the tank will go, My current tank is sitting on cement and that also is another reason for the size I picked. It had to fit in that spot and be able to get in the door.

yeah the door thing sucks. You could always install double doors in your home... see how your wife take that one

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12779287#post12779287 target=_blank>Originally posted</a> by marinelife
I will be putting supports in the corners and bracing around the top of the tank. I have spoken with several tank builders and several plywood tank builders and they feel with the two plywoods glued together and the epoxy/fiberglass I should have more than enough thickness to hold it together. I have not seen many large deep tanks and even less made out of wood so I am kinda going into the unknown. If I was to get them make out of just acrylic they would use 1.5 to 2" thick sheets only.

I've built a number of plywood tanks, up to 520 gallons, and headed up several of the plywood tank building workshops that were sponsored by local fish clubs in the Cleveland area. I've also repaired a lot of plywood tanks that other people built. Usually there is some logic that explains why some things work and some don't, even things that are not obvious at first. However one very consistent thing I've observed but can't fully explain, is that every single tank that I have seen that was built with doubled plywood -- leaked! It may have something to do with one other observation.

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12778681#post12778681 target=_blank>Originally posted</a> by hebygb
I would strongly rec. reinforcing the sides... over building would be the way to go. I would almost build the walls as if you were building a wall to a house only using plywood instead of drywall. This will prevent bowing... may even advise to use 4x4s or doubling up the 2x4s. ...

I've built 2 by 4 walls on 16" centers around taller tanks, but not attached to the tank. that just makes for lak opportunites. I would never use 4 by 4's for this. 4 by 4's are very prone to twisting and bowing because they tend to be still wet inside. They are also often treated, which is not for interior use. Different types of treated wood give off different toxins, but you still do not want them in your house near you, your reef tank, or your children. Two 2 by 4's with a "sandwich filling" of half inch plywood makes a much stronger straighter, more durable support with equal dimensions.

No one has yet answered the starting question, what is the best plywood for this job. It is not marine plywood. That's good, but its claim to fame is not the glue type, but that the voids inside are filled. It is not BC exterior, although that makes serviceable shallow tanks and sumps. It sucks up the paint or fiberglass resin, so the savings you thought you saved, get sucked up out of your expensive paint cans.

The best plywood for tanks is 3/4" MDO plywood core signboard. It is stiffer than normal plywood, but not really stronger. Stiffer is what we want though, in order to minimize flexing as the tank water levels change. MDO has a dense pressure and heat applied coating that lengthens the normal life of the waterproof coating you put on it, so a 20 year resin just might last 40 years. it is also much smoother than regular plywood, so it's easier to end up with a final smooth flat surface.

 

[marinelife]

Thanks for the post, I would really need more information other than they leak!!!
Where was the leak how big was the tank, etc....

I was told by several people the MDO would fall apart.

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12793965#post12793965 target=_blank>Originally posted</a> by marinelife
Thanks for the post, I would really need more information other than they leak!!!
Where was the leak how big was the tank, etc....

I was told by several people the MDO would fall apart.

That they leak should be enough information to make a saner choice. Every doubled plywood tank I have seen, even prefessionally built ones, leaked at the seams. All of the doubled plywood tanks at the Falls of the Ohio leaked. There was so much leakage that plastic rain gutter was used to collect the saltwater and drain it to the sump in what turned out to be a temporary marine exhibit complementing the Devonian fossil beds on the musem grounds. http://www.fallsoftheohio.org/

Every tank where a tank builder tried to double the panels or to double the inner seams with a square or triangular piece to "add another seal" to the seam has leaked. I suspect the problem may have to do with the odds. Every time you add another seal, you add at least one more seam which could leak, and many more connectors, each risking another opportunity for a leak. Double the risk by doubling the connections, and that would explain why doubled tanks leak would more often than normal ones. It still does not explain why they seem to be 100% leakers.

Several people told you MDO would fall apart. That is a crock. Maybe you should ask them what were their motives for making something up that just proved they know nothing about what they tell you. The MDO was suggested to me by a professional aquarist who showed me a piece of MDO that he had submerged, unpainted and with raw untreated edges, in a marine tank for one year. Dried off, it looked new.

Hopefully your people just weren't listening to you and thought you said either Masonite OmniWood, or MDF (medium density fiberboard). The Omniwood had some performance problems. if you believe the lawsuit. MDF is not a plywood and although it may have some uses around water, the edges, even well sealed, will swell over time, certainly not something you would want happening at an aquarium seam. There are commercially made low end stands and canopies made with MDF. I haven't seen any of them fall apart, but I have seen them looking really ugly after less time than I would expect to keep a stand for.

 

[marinelife]

Well I have birch and fir already and the tank has the side wall and back already glue together. I looked and the place I purchased my wood from has MDO wood, not sure the price but I can not switch now. I know of a few tanks that are double layer that are not leaking.

How long do you wait to see the leak start?

 

[Rhodophyta]

I believe most of them probably leaked from the start, but because of the nature of plywood, when there is a leak, the wood plies that get wet swell up and temporarily seal off the leak. As the wet wood deteriorates, a "new" leak starts, then self seals again. Many plywood tanks I've repaired had signs of that on again off again leak pattern. The owners at first thought they did not have a leak, just spilled water since there was no sign of further leaking, or they didn't even see the water if it was at the back of the tank, until months had passed and the leak became constant.

I have always been afraid to fix the doubled tanks since they fail so often. It seems to me if you doubled the panels first, then assembled the tank as if it were made of 1.5" plywood, you would have a better chance of sealing the tank. When you cover a previous layer of plywood, you might explain some leaks if a new screw hit an old one and bent, creating a avenue of escape for the tank water. Use wood screws, not deck or drywall screws.

And then there were products out there that could turn a cardboard box into an aquarium. Upgrading your paint inside should help, or using several more layers of epoxy and fiberglass.

http://www.sanitred.com/waterproofing-blog/archives/category/pondfountain/

http://www.housesofthefuture.com.au/hof_houses04.html#whychoose

 

[marinelife]

Thanks for the reply and knowledge. I guess the way I look at it is seal it well so it does not leak. If it leaks the board I use does not matter anyway becuase I would have to drain the tank and move it out and get something else, not wood.

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12799493#post12799493 target=_blank>Originally posted</a> by marinelife
Thanks for the reply and knowledge. I guess the way I look at it is seal it well so it does not leak. If it leaks the board I use does not matter anyway becuase I would have to drain the tank and move it out and get something else, not wood.

Well the wood used does make a difference to the success of the project, in terms of savings over an all glass or acrylic commercial tank over the lifetimes of each for a fair comparison. I understand how you are looking at it, but one reason the plywood tank has become less popular is that glass prices have dropped and wood has gone up for the past decade or so, eroding this as a way to get a huge tank for much less.

Another personal factor was a trip to Dr. John Miller's biology lab one fish club meeting. He had, among many larger and more impressive marine tanks, a glass tank with several inches of muddy looking stuff on the bottom, like fine brown sand. In the tank were shipworms. They were neat, but the sheer amount of wood he fed them was incredible. Considering all the damage they could do to wooden ships back in an era when heavy metals and toxic materials were in common use to protect what was then an invaluable economic asset, what could that invert or some other less known ones, do to a plywood marine tank? After that fish club trip, I don't believe there were any more sucessful plywood tank workships here. Interest dropped fast.

Another drawback to a plywood tank besides not being a wise choice for keeping shipworms.... My daughter borrowed a 120 plywood tank from me for her dorm room. After tiring of the fish tank, she converted it, as she had done with some glass tanks before, into a home for her pet rat. It tunneled right through the side of the tank.

 

[ncwaterboy]

Epoxy is thermoset plastic, if applied to the wood correctly, especially in conjunction with fiberglass cloth it will provide an effective barrier against ship worms. I live in eastern North Carolina, the center of the Universe in terms of wooden yachts built with epoxy coatings and I can attest that they hold up very well in a demanding Marine environment.

 

[BlueCorn]

...

 

[norskfisk]

I don't really think rats and shipworms are a general problem for aquarium owners. In that case people wouldn't be able to have acrylic tanks or pvc tubes since these are softer than epoxy.

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12805188#post12805188 target=_blank>Originally posted</a> by norskfisk
I don't really think rats and shipworms are a general problem for aquarium owners. In that case people wouldn't be able to have acrylic tanks or pvc tubes since these are softer than epoxy.

Thanks for reminding people that rats and shipworms are not a general problem for aquarists with plywood tanks. There could have been someone who misunderstood how unusual either could be. In the first case you have to put shipworms in your tank. In the second case you have to loan a tank to a teenager. :mixed: Of course now that you mentioned it, I have to get rid of my acrylic tanks now and the plastic plumbing from my filters.:mixed:

 

[norskfisk]

There was a time, back when I was researching for builing my first tanks, when I considered the possibility that some tank inhabitant might chew their way through the plastic. After all some urchins have been documented to chew through concrete, some clams bore in rock, and I am sure there are other animals too that have strong jaws and various types of chemical attacks. If a plywood tank has only a thin layer of epoxy, maybe poorly mixed epoxy, and has holes where the smell of rotten wood comes leaching in it wouldn't surprise me if something could gnaw the hole larger. But this is only an issue if the tank is of extremely poor quality in the first place. Chewing tank inhabitants is not something you have to worry about if you take the construction seriously.

 

[Rhodophyta]

<a href=showthread.php?s=&postid=12809590#post12809590 target=_blank>Originally posted</a> by norskfisk
There was a time, back when I was researching for builing my first tanks, when I considered the possibility that some tank inhabitant might chew their way through the plastic. After all some urchins have been documented to chew through concrete, some clams bore in rock, and I am sure there are other animals too that have strong jaws and various types of chemical attacks. If a plywood tank has only a thin layer of epoxy, maybe poorly mixed epoxy, and has holes where the smell of rotten wood comes leaching in it wouldn't surprise me if something could gnaw the hole larger. But this is only an issue if the tank is of extremely poor quality in the first place. Chewing tank inhabitants is not something you have to worry about if you take the construction seriously.

I have a plywood tank that has been set up as a reef tank since the early 80's. It must be nearing the limits of its life and should be repainted or discarded some day soon. It has had urchins, snails, crabs, and chitons among others that might chew but is still OK although some of the original four coats of Palgard epoxy may have been abraded over the years in spots.

However, using a plywood tank as a cage or terrarium for rodents, some insects and terrestrial plants is still a poor choice. Also in fresh water aquariums, there is at least one fish whose "pleco poop strings" will be whatever color a plywood tank has been painted with.