# Is a polycarbonate aquarium feasible?



## Fish Jerk (Mar 9, 2016)

Hi guys, I registered mainly because I have seen great DIY stuff here like the acrylic tank guide.

However acrylic is ****** expensive once you need to get to thicker grades of sheeting. Since I am not a DIY pro I would hate to spend 100+ bucks for a bunch of acrylic sheets then render them useless due to my incompetence.

OTOH Polycabonate (Lexan) is about 25-50x stronger than acrylic so this got my gears grinding. If this is the case then perhaps I could use a thinner (and therefore waaaaay cheaper) polycarbonate sheet instead. However, I notice that there is no such thing as a polycarbonate aquarium let alone a DIY polycarbonate aquarium. Is there some reason for this or is it just because Lexan used to be so expensive or that people are not as used to working with it yet?

The only thing I can think of since it's so extremely strong is maybe it is too bendy ie it is not hard enough to keep its form - which is also a problem with plexiglass of course. But there is also a version called makrolon that is more expensive but should be much much harder due to being impregnated with fiberglass.


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## Fish Jerk (Mar 9, 2016)

https://www.tapplastics.com/uploads/pdf ... 20Data.pdf



> MAKROLON
> ®
> AR
> polycarbonate
> ...


This description is promising. Glass like hardness is exactly what's needed - this is probably why there are no polycarb tanks.

From what I gather you use similar kind of bonding for polycarb as with plexiglass btw.

http://www.usplastic.com/catalog/item.aspx?itemid=24785

I see some square foot sheets here for just 5 bucks each!

2 feet by 4 feet for 40 bucks.

This stuff is probably uncuttable without very special tools, but you should be able to get sheets in a reasonable size.

Say make a 48" x 24" x 24" aquarium.

4x 2 feet by 4 feet = 4x40 = $160.
2x 2 feet by 2 feet = 2x20 = $40.

total = $200 for a nice 120 gallon tank.

Or you can double the gallons and width for an extra $160 and get a 240 gallon tank for $360.

Of course, not that I think of it, if you can't cut it then you will have to do something different for the top. If it truly has the hardness of glass and that much strength maybe it could be left rimless.


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## Narwhal72 (Sep 26, 2006)

Polycarbonate is not as clear as acrylic or crystal styrene which is why it is not used in aquariums. There is a lot of distortion in the material. Like looking through glass covered with vaseline.

Also you need to use a thicker wall material to keep it from flexing and bowing. A 24" tall acrylic aquarium would need to be at least 1/2" thick.


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## Fish Jerk (Mar 9, 2016)

They make windshields out of polycarbonate.

The makrolon claims to be as hard as glass. I guess there's no way to be sure unless someone has direct experience though.

As for bending, even if you have a material that bends shouldn't that be something you can take care of with a frame? The main problem with bending is that it leads the material to break which is why glass and acrylic need to be so thick.

Another thing with makrolon is that it is coated which might present a problem.

I did read of someone making a 12"x12" cube lexan tank with some silicon gel after roughing the edges. I don't know any details though and no followup.


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## Fish Jerk (Mar 9, 2016)

Ignore the last post. I tried to edit it, but could not.

They make windshields out of polycarbonate. There are many grades of it, the opaque ones are cheaper but not really even that much cheaper.

The makrolon coated polycarbonate impregnated with glass fiber claims to be as hard as glass. I guess there's no way to be sure unless someone has direct experience though.

As for bending, even if you have a material that bends shouldn't that be something you can take care of with a frame?

The main problem with bending is that it leads the material to break which is why glass and acrylic need to be so thick. But polycarbonate is very difficult to break. So I would hope this issue can be either overcome with a frame or by using makrolon (which is actually cheaper than untreated polycarbonate).

Another thing with makrolon is that it is coated which might present a problem. But again I wonder if a frame would take care of this. I think in a silicon seal you are basically just setting it in cement anyway not really truly bonding the stuff - so if it works with glass it should work with polycarbonate - if you either have a big enough frame to prevent bending or a hard enough form of polycarbonate. Of course like I said hands on experience is the issue here. How do you even ask how bending a product is?

I did read of someone making a 12"x12" cube lexan tank with some silicon gel after roughing the edges. I don't know any details though and no followup. But I don't think he even used a frame.

Not being able to cut it easily makes for a bit of a problem though.

I guess maybe something like making 5 sides with makrolon and then the top with half inch acrylic would be necessary. Or else a metal frame.


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## Narwhal72 (Sep 26, 2006)

A windshield and an aquarium are different things.

I actually have experience with making polycarbonate aquariums. We have looked at making Minibows out of polycarbonate in the past. It never comes out as clear as crystal styrene and other than R&D samples we tested, it's never been used in production. The tanks look terrible. And those are small desktop tanks. I couldn't imagine how bad it would look on a thicker, big tank.

A frame will only reduce the bowing at the top. But the center of the panel will still move out quite a bit from the water pressure. A typical glass aquarium will bow out in the middle about half the thickness to the full thickness of the front panel. The glass doesn't stretch or get longer, it pulls it in from the sides. Silicone allows a flexible seam which allows for this. For acrylic and polycarbonate which are glued with a inflexible seam, the bowing of the panel actually causes the material to stretch. If the bow is more than the material can stretch the seam will pop or the panel will crack. Which is why you need to use a thicker panel to reduce the amount of bow and keep the sides from popping.

Believe me, If polycarbonate was a lower cost alternative to making acrylic (or glass) aquariums. We would have done it by now.


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## Fish Jerk (Mar 9, 2016)

Obviously the standard polycarbonate can't be used for much of anything but a water bottle that slowly poisons you. But there are coated types that can be used for clear windshields, bulletproof glass that is very clear and so on. I mean, I can just look at the glass and see it can be done.

If I used a frame then it would be for all the seams. According to the one site selling it, the same silicon stuff they use in aquariums would be fine for boding either glass or acrylic or polycarbonate mix and match.

The flex is what I worry about mainly, especially if it pulls from the sides. Actually if the seam were of the pure joining variety I would not worry too much since it's basically same stuff as the polycarbonate itself and should bend quite a bit. But I am not sure that approach will work out too well with a coated substance. It probably won't work. Some of it I see is coated on just one side though.

Looks like the GP version I linked to is not what I want, though. I probably want either AR or WG (window grade). But the WG is very thick and therefore expensive and I can't find AR available in sheets.


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## Fish Jerk (Mar 9, 2016)

Looks like the AR starts off at 1/4 of an inch thickness and is much more expensive.


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## Fish Jerk (Mar 9, 2016)

I have a stand that is about 100 inches x 20 inches granite top beveled sides. I used to have a large glass tank on there and one smaller one. Like 150 gallons and a 20 gallon, something like that. I got rid of it because I had to move and it's extremely heavy.

Now I have a 55 gallon acrylic and a 55 gallon glass aquarium that has a sagging support brace in the middle. The acrylic one is nice but the other one I worry about and would like to get rid of. Maybe give it away to someone for a reptile cage.

Ultimately what I would like to do is build two aquariums that are each 48x24x20 giving roughly 90 gallons capacity for each one and a total of upwards of 180. In addition I want to build a clear bridge connecting them.

I was thinking this would be 12" x 12" cube with tubes running downward from each side of the bottom, with the cube resting up out of the water between them. Right now I have a plastic tube connecting them in this manner, but I want something that is inflexible and goes down further but doesn't look like poop. Right now the filter intakes are all on the same side and the outputs on the side that has all the plants. That way there is no problem with sucking in plant matter into the filters, or losing fry or baby shrimp etc.

So for now what I would want to do is to try and make that bridge part. Should be easy to manage that with standard acrylic, but if there is a better material I am willing to give it a shot. That is why have been looking at the makrolon. I am not so sure now this will work out well for a big tank but maybe I will give it a try with making the bridge.


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## Narwhal72 (Sep 26, 2006)

Silicone can not be used to seal a polycarbonate or acrylic aquarium. Silicone does not bond to plastics as well as glass and the seal does not hold. You need to use a proper glue (Weld On #16 works well) to bond plastics.


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## Fish Jerk (Mar 9, 2016)

I don't think anyone really knows that, but as I said already I know at least one tank was made in that way after roughing the edges a bit. It should not really even matter that it is very strong, so long as there is not too much deformation. And if there is it won't be enough to stop it from popping.

Anyone know if it matters whether pieces rest on the bottom or not? Would one where they are on the sides of the bottom piece be OK or will that cause it to leak.


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## Fish Jerk (Mar 9, 2016)

Also, poking around a bit more I heard of a large polycarbonate cylindrical tank in use at some pet store. One piece of very large polycarbonate tucked into a wooden frame in the back. Not ideal for large tanks unless you can manage to find very large sheets somewhere, but if they were able to use a thin enough sheet for it then it might be worth looking into.

For putting polycarb into a frame (or any material really) silicon should be A-OK, or else you would be out of luck for making a tank like this one (or using acrylic windo in a plywood tank....). For adhering it to itself with no support it is another story and is not something I would even try.


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## Narwhal72 (Sep 26, 2006)

Plywood and fiberglass stock tanks used in aquaculture sometimes feature a polycarbonate or acrylic viewing panel. But you are right that it is the frame around the panel that is providing support. The panel is pushing against a silicone or epdm rubber gasket that is between the panel and the frame of the tank. Sometimes there are screws or bolts actually holding the panel in place. Since there is no seam that needs to be held together it will not leak or separate.

I have worked with several acrylic manufacturers and they will tell you straight up that silicone will not hold a plastic tank together. I would trust people in the industry with years of experience.


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## Fish Jerk (Mar 9, 2016)

Narwhal72 said:


> Plywood and fiberglass stock tanks used in aquaculture sometimes feature a polycarbonate or acrylic viewing panel. But you are right that it is the frame around the panel that is providing support. The panel is pushing against a silicone or epdm rubber gasket that is between the panel and the frame of the tank. Sometimes there are screws or bolts actually holding the panel in place. Since there is no seam that needs to be held together it will not leak or separate.


That is good info, thanks.



Narwhal72 said:


> I have worked with several acrylic manufacturers and they will tell you straight up that silicone will not hold a plastic tank together. I would trust people in the industry with years of experience.


Every material is different. It was listed as a mixed use adhesive on the one site I linked earlier, though, and someone else apparently did this with at least temporary success. Nothing is going to say "good for aquariums" because no one is using it for aquariums and it would take a large amount of testing to say something like that with confidence. But a self bonding with no frame is not going to be strong enough probably anyway, for a large tank, due to the noodliness. I guess that the poisson ratio is .38 whereas glass is around .2 or something. Not sure what acrylic is, but I assume in between somewhere. I wish I had some samples to judge for myself.

Maybe if you had it bolted into a frame with a rubber gasket, into each face, and sealed?

Looking around it seems this stuff might be better for such a purpose. http://krayden.com/lord-40619-acrylic-adhesive/

I am not confident enough to try a big tank but maybe I will try to do that bridge and see how it works out.


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## JasperMagi (Apr 24, 2019)

I don't build "fish" tanks, but I do build tanks for other uses. This tank is Makralon GP I believe. It has kind of a grey colour to it. I just use the same Weld-On flavours that you would use with acrylic. I use polycarbonate where I am worried about mechanical stresses or chemical attacks on the tank. This tank is used for pressure testing a plastic valve body at around 250 PSI, and has to be able to hold shrapnel and potentially brass plugs shooting around the tank. The aluminum frame is simply to ensure that the tank is not damaged when moving it around in an industrial environment. This one is 3/8", but I could have easily gotten away with 3/16" and still not had to worry about projectiles exiting or the tank or the sides bowing (even without the frame). I used 3/8" because I wanted a thicker bond line for resilience in an industrial setting. The material does bend much more than acrylic, but it's also much less delicate to work with. It does not cut well with a laser, and can similarly build up heat and melt back to itself during machining operations. Using clean water as a cutting fluid will keep it cool, and keep it from fusing to itself or tooling. Hope this helps someone down the line somewhere.


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## BlueSunshine (Jul 13, 2014)

Fish Jerk said:


> https://www.tapplastics.com/uploads/pdf/Polycarbonate%20AR%20Product%20Data.pdf
> 
> 
> 
> ...


You should read this again. It doesn't say "as hard as glass".


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## ken31cay (Oct 9, 2018)

Sounds to me like the feasibility is in question. Everything I've googled indicated it is more expensive than acrylic, also read it scratches easier than acrylic and that for me is the only drawback of my two acrylic tanks vs glass.


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