# Making a Monster Tank Lined with Plexiglass



## bntbrl (Apr 23, 2009)

I was looking through some other threads and other topics and ran across some people that used panes of glass, panes of plexi, and even marble and granite slabs to make the inner walls of their homemade tanks waterproof.

Epoxy and or fiberglass and mat are an obvious choice. However the flex of the tank, rocks abrading the coating, and wear may compromise the fiberglass or epoxy. This is where the liner with plexiglass would come in.

Does anyone see a problem with building a plywood tank and using plexiglass on the bottom and sides? Then the glass would fit over that in a way that it wouldnt compromise strength?

I have not built a tank of any size with plywood. I was considering a 6'x3'x3' or so. I have not made any plans yet as to glass thickness or structural integrity. I have only been entertaining the idea at the moment and will start researching plans and glass thickness.

Is there a way to use the plexiglass on the viewing side and have the glass/acrylic flat on the surface so that no additional stepping from the side to the glass is necessary? I also am looking for the strongest way to make the corners of the sides meet. *** seen some terrible ideas and *** seen some that are bettter than others. I would think that using a framed wall construction would be good, then bolt the sides together with 2 2x4s filling the gap in the corners on teh outside. Then put plywood on the outside to hide the framing. With the 3 feet depth I would accept that there would be a space below the glass viewing of some distance that is plywood for both strength of the structure and the glass.

Any thoughts?


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## Toby_H (Apr 15, 2005)

Plexi sheets are expensive... so is glass... if I read your post right you are considing using both, which would be very very costly...

Keep in mind silicone doesn't adhere well to Plexi... and blastic adhesives do not adhere well to glass... which is why it is difficult to incorporate both in the same construction...

I've toyed with concepts of building a massive DIY tank... and I've talked to others with first hand experience...

My suggestion is to read through the many threads of people who built tanks in the size range you are considering. They usually share not only what they did but what they would have done differently.


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## Stickzula (Sep 14, 2007)

One problem that you may run into is the cost of the acrylic compared to the price of epoxy. I haven't priced either, but I know from past projects that acrylic can get expensive especially with larger pieces.

Then the next hurtle would be sealing the tank. Ideally you would use weld-on to adhere the acrylic together, but if there are any gaps between the joints it won't work very well. There is a weld-on product that is fairly thick, but I haven't priced it and I don't know how big of a gap it would fill.

The last thing to worry about is attaching the glass. Obviously you could use acrylic and use weld-on to adhere it to the rest of the tank, but glass is usually cheaper. The problem with using glass is that weld-on won't adhere it to acrylic and silicone doesn't stick well to acrylic. A gasket and retaining frame are usually the answer to that.

A side note that will apply no matter what you use, assuming that you ever want to move the tank. You should make the size so that by turning the tank at least one way you can get it to fit through a doorway. The largest standard door that I know of is 36", but that size is typically used in commercial buildings. The common size for exterior residential doors is 30" with some being only 24". My advice would be to make it so it would fit through a 24" doorway. A 24" width or height would be pushing it, but I would feel fairly confident that you could get it through most residential front doors.


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## bntbrl (Apr 23, 2009)

I dont think that Id be interested in moving it. Its something that I considered. Id be okay with having to sawsall it to get it out. Id likely leave it there unless whoever buys the house whenever we decide to sell it would like it taken out.

I had read some other posts but I couldnt find these topics readily discussed. Ihadnt thought about the silicone and glass thing. I suppose that if it were built using acrylic window it could be sealed using weld-on. I have used some of the acrylic sealers on small projects a long time ago like sumps and what not. I had the thin stuff so my measurements had to be pretty close without gaps.

I have a freind that is a glass guy and he has some plexi available that is scratched. I dont know how to seal the window with glass. I guess I can try to barter for glass panes to line the tank with and seal it all with silcione but Im not sure how Id fit the viewing side as it would have to be cut or double paned with a thinner glass.

Sounds like epoxy is likely the cheapest route and easiest. I can get some glass cheap and some plexi cheap (maybe free or barter with him). But I dont know how Id get it finished using only those materials.


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## Mcdaphnia (Dec 16, 2003)

If you can get glass cheap enough, an all glass tank in the dimensions you want should not be a problem to build with silicone. And probably one of the best solutions since glass lasts a lot longer than plywood and compared to any of the materials you mentioned needs much less maintenance.

Resdiential entry doors are usually 36", but trim and the door narrow up that dimension a little. Either a double entry door where both can be opened, or a large window that can be opened, or at worst, removing a large window temporarily would get the tank out when needed, even one much larger than yours. When we sold a 520 and 250 that had been built in the fishroom, we made a big hole in the outside wall and walked them out, then put new studs, insulation, and cedar planks in the hole and re-drywalled inside.


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## bntbrl (Apr 23, 2009)

As far as the glass goes I kind of get what I can get. Even at a discount the glass for a ginourmous aquarium would be inhibitive to me.

I think my wife would get PO'd if I cut a hole in the wall to get my tank out of there lol. Im not that concerned with having to dissassemble it later if the need should arrive.


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## Toby_H (Apr 15, 2005)

Typically in the US... exterior doors are 36"... interior doors are 30"... some doors are 24", but they look/feel/are tiny.

Personally, I would make one of the dimensions 29"... either height or width...

Cichlids don't need a depth of more than 29" anyway, so with them you aren't loosing anything... although there are other types of fish that may appreciate the added depth... and visually speaking, well a lot of different things can look cool...

I would discourage you from making it in a way that would make it impossible to take out of the house without deconstructing it just to have 7 more inches of depth... I just can't see it being that important...

But if you are confident that you are going to be in the same home for as long as you are going to care about having this tank... then I could understand ignoring my suggestion...

...lol, I'm sitting here wondering how many men have said to their wives... "oh come one, it's not like I'm cutting a hole in the side of the house"... and then wondering if McDaphnia realizes how awesome his wife is for letting him do just that... lol :thumb:


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## zazz (Apr 5, 2008)

maybe before you build this huge structure you should go back to basics ... maybe you do not need such a huge piece of transparent interface between you and the fish... is it really necessary??


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## smulder (Jul 6, 2007)

I may have misunderstood what you were describing, but it didn't sound to me like your idea has been really addressed, and it is one I'm curious about as well. My understanding is that you're talking about using plywood for structural integrity, and then a very thin layer of acrylic just for water-proofness. Very thin acrylic is actually pretty cheap. Any problems with this idea?

One idea is that instead of using glass for the viewing window, you could just buy a single thick piece of acrylic and then bond it with the thin acrylic coating the inside for a window. Does that make sense? This seems like it might work and might even be cheaper than using fiberglass/epoxy.... not to mention potentially easier to bond using standard acrylic-on-acrylic bonding.


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## bntbrl (Apr 23, 2009)

I was thinking about using 1/4 inch acrylic as a waterproof layer. I also thought about making the viewing area acrylic as well. It would have to be cut to pretty exact size to avoid gaps int eh acrylic sheet.

One thing is that after framing the viewing area one could use a router to remove the window of acrylic sheeting and use acrylic strips to position the viewing pane on the viewing side. Then the gel type weld on could be used to seal the viewing window to the 1/4 thick sheet.

Im not sure what would be best to adhere the thin sheets to the sides. Silicon might work and would allow one to position the sheets into place proplery as opposed to something messy like grout or another underlayment.

I think Ills tart making some diagrams. Does anyone have any idea of what software people use to mock these things up? I have photoshop but if theres something I can make board lengths with and move them around taht would be great. *** seen some tank stand diagrams that were like cad drawings but Im sure that they were drag and drop.

I dont really need as big of a tank but I feel like this is a one shot deal pretty much. Go big or go home might apply here lol. I can make it much longer, say 8 feet and make is shallower, like 26 inches but leave the bottom 36 so that I have a good footprint but it might make it out the basement stairs.


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## Rivermud (Nov 22, 2004)

It has been thought of and discussed many times. There are drawbacks. First, if you have just one itty bitty leak you will end up with a mess. Second, plexi is not cost effective, there are many options available to seal a large aquarium that are the same price if not less expensive and do a better job. I don't mean to discourage the creative thinking, just giving a fair warning of the issues involved with this idea. I would suggest alternative waterproofing measures. By the way, generally any tank under 200 gallons is probably cheaper than what you can build it for out of plywood and sealer.... not always but generally.


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## prov356 (Sep 20, 2006)

> I was thinking about using 1/4 inch acrylic as a waterproof layer. I also thought about making the viewing area acrylic as well. It would have to be cut to pretty exact size to avoid gaps int eh acrylic sheet.
> 
> One thing is that after framing the viewing area one could use a router to remove the window of acrylic sheeting and use acrylic strips to position the viewing pane on the viewing side. Then the gel type weld on could be used to seal the viewing window to the 1/4 thick sheet.


What I'd suggest is that you put this together just as if you were building a typical acrylic tank, but with thinner material for back, sides, and top. Use the watery weldon 4, not the thickened weldon 16. You can then use a thickened solvent to seal the inner seams, if you like, but not necessary if put together properly. I would add the extra step though just for the extra peace of mind. I thicken the weldon 4 with some acrylic shavings and then run it along the seam with the applicator bottle. When the solvent evaporates, it leaves a thin layer of acrylic in the seam. It works well. I can give more detail if you decide to go with this.

The only difference between what I'm suggesting and a standard acrylic tank is that you're using thin pieces for sides, back, and bottom. Go full thickness for viewing pane. I like the idea of 1/4" for the back, sides, and bottom. Any thicker and it's gets much more expensive, and any thinner would make it hard to work with. You can, of course, improvise with the top and use strips instead of the full top.

Once it's together paint back, sides, and bottom, and then frame snugly with 2x4's to provide for the structural support that the 1/4" acrylic won't offer. No need for the plywood. You could use a thin foam between the tank and frame. If the acrylic bulges a bit because there's a small gap between tank and framing, it's not big deal. You're just trying to avoid excessive bulging. All acrylic tanks bulge a bit. It's actually not unusual to do this even when building typical acrylic tanks. The bottom piece is sometimes made from thinner acrylic since it's supported by the stand.

If done properly, it should hold for a long, long time, and would save you money over what a typical acrylic tank would cost. Not sure how it would compare to going with plywood and epoxy instead. It'd probably be a good choice for someone who came across some free or cheap 1/4" acrylic and wanted to make a large tank.

I agree with Rivermud that if you go DIY, go big. Otherwise might be easier and cheaper to just go buy. Doesn't have to be deeper or higher. Think 8 to 10 feet long instead of 6 feet. 8' x 30" x 30" is 375 gallons and will fit through the doors. Build it so you can remove the acrylic tank part out of the framing. Even if you had to redo the framing, it's the acrylic that's expensive. 2x4's are cheap.

Just as an aside, I don't know of anything that will seal acrylic well except the acrylic solvents and those only seal acrylic to acrylic.


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## bntbrl (Apr 23, 2009)

The 1//4 inch plexi I can get for nothing. It is abraded in various places cosmetically. He has 6 sheeets he knows of and thinks he has 2 more. Id have to buy a peice of acrylic for the viewing area if I couldnt find something depending on the size and thickness. Id have to buy the wood, the glue, and screws and things like that. At 6 x 3 x 3 thats 400 gallons. At 8 feet thats 538 gallons.

As far as having a leak would be hard. You mean where the corners meet and are sealed withthe glue? Or you mean in general? I cant see it being much fun anyway.


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## Rick_Lindsey (Aug 26, 2002)

Heh, i'd buy a clear piece of 1/4" acrylic and cut it into four 8'x1'x1' windows, and build a bunch of loooooong 120 gal acrylic tanks (8'long, 2'wide, 1'tall) for gobies and shellies! No wood needed!

-Rick (the armchair aquarist)


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## bntbrl (Apr 23, 2009)

I wonder if it would wobble like mad if you bumped it? I never had any shallow tanks. Id rather have a big on.

If I made it 8 long and 4 x 4 that would be about 958 gallons. I could use the whole sheets without cutting much. Theres a lot of stuff to take in to consideration. Its almost overwhelming on where to start. The structure, the viewing medium size and thickness. Then plumbing and lighting the thing.


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