# Being the thinker I am... would this work?



## halffrozen (Sep 24, 2011)

So, I have mentioned either here or another forum that I am a water-jet programmer/operator.

I also work with rigid plastics, MAINLY HDPE, LLDPE and other forms of the two. We have a sheet of 1/4" Plexiglas that I have used to cut out custom tank tops for my 36gallon Bow-front and 40Gallon breeder... Still a bit of usage in it...

After reading over all of these cheap ways of making tanks out of wood, and what not.. I thought.. we build these **** tanks for my work!!! lol just out of plastics, that can handle alot of weight and all that.

So... We have the machinery to make a FULL 4 sided box completely into ONE solid piece, would just have to extrude on the bottom, and cut a hole in the tank where the Plexiglas will go on the front...

Would this even work, I figure we HAVE gotten some orders made for hatcheries, I wouldn't be surprised if we have made some for LFS's in my area/state.

So anyways.. we have FULL sheets of almost any type of plastic that is left over from jobs, my thoughts would be maybe... about a 100g or maybe just make a small one for now to see how it holds/reacts with fish?

What are the "dream" dimensions for tanks exactly?

Will post what the tank will generally look like soon.


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## nodima (Oct 3, 2002)

Everyone's dream tank is different. Factors such as cost, placement in house, etc. all come into play.

For me, without being in a dreamworld, I'd love one 6' long, 30" front to back, and 18" tall. This is essentially a standard 150 rotated 90 degrees.

YMMV


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## The King Crabb (Jun 28, 2011)

I'm a little confused on the question, you're asking if you can subsitute the plastics you work with (are they opaque?) with the wood? If so then I'd assume they would work so long as they don't leak toxins and will hold the weight. I'd make a smaller tank (possibly without plexiglass if you want to save some of that) to make sure it doesn't leak toxins, about 10G-20G and just put some cheap fish in there like zebra danios.

Like Nodima said, everyone's dream tank is different. Personally I'd love a tank that's 10' tall and goes all the way around my shower, it would seem like i'm showering with my fish!


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## halffrozen (Sep 24, 2011)

Sorry I was a a few wine bottles under last night and was surprised I was able to type all of that.. lol

Question I think is... is HDPE safe for fish? And how would one go about making a complete and ever lasting seal between HD and Plexi?(what type of adhesive, would think a normal Marine Epoxy would do.. just wanted to make sure)

I could give a small tank a shot and test it on some feeders... Will have my guys make up a 10-15gal when we have a dead spot in our week.


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## The King Crabb (Jun 28, 2011)

Not sure on whether or not HDPE is safe for fish, that's what the test tank will be for.

The seal will be a little bit tricky, since silicone doesn't really stick to plastic too well. With wooden tanks you usually make a sort of "frame" so the water pressure just keeps it there and then you silicone it in place so it won't move, that sucker won't come out unless you drain the water and punch it out. Not sure how well that would work with HDPE though.


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## CITADELGRAD87 (Mar 26, 2003)

What if you just made a slide in frame using the HDPE, slide the plexi in, then seal it in place. You're the waterjet guy, would that be possible? Can you glue HDPE to itself?

That would be just like the water pressure in a plywood tank, right?


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## The King Crabb (Jun 28, 2011)

CITADELGRAD87 said:


> That would be just like the water pressure in a plywood tank, right?


I had the same idea, and I believe it is basically the same thing. But like you, I'm not sure how the plastic would hold up to that.


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## CITADELGRAD87 (Mar 26, 2003)

Yeah, it's pretty easy to spitball when it's someone else's floor that might get drenched.

I have no idea the properties, but if it is being considered as the main body of a tank, it should work.


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## halffrozen (Sep 24, 2011)

The rigidity of the plastic will be fine so long as it isn't a 3" deep tank. With taller walls we usually put girth supports.

With HDPE we thermally weld the two pieces together, so they will become one piece when we are done. 

That slide in Plexiglas is exactly what I was thinking after looking at the scrap we have today...

We are definitely able to router a 1/4" channel, no problem there...

Its all on the adhesive, even our main tank guy was saying there a few sealants that are plastic friendly, and then they have to be fish friendly! lol

So to recap, everything we are able to do... but it all comes done to the seal between plexi and the HDPE or the Co-Poly...


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## The King Crabb (Jun 28, 2011)

It really comes down to the strength of the routed channel, that's what's holding in the glass. If you feel confident the sides will hold, do you also think that a little channel will hold in the tank glass just fine or will you need to make it much deeper?


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## halffrozen (Sep 24, 2011)

I figure a 1/4" to 1/2" deep channel should suffice. I would think to ensure full tank rigidity, I would add a brace that goes around the FULL top ID, as a single piece(for better support).

We will see once I get the time!


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## ls5292 (Jan 24, 2012)

Would plexiglas work for a tank top and put a strip on top of the light that may or may not set on the brace and the side of the tank


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## jchild40 (Mar 20, 2010)

ls5292 said:


> Would plexiglas work for a tank top and put a strip on top of the light that may or may not set on the brace and the side of the tank


I had problems with plexiglass as a top. It starts to sag after a few days.


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## badspellar (Oct 14, 2009)

Your original question asked if hdpe is safe for fish. I believe it is. After all hdpe is used for water supplies, so its safe for people.


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## halffrozen (Sep 24, 2011)

Odd, it doesn't show that this is MY thread on the index... but ok.. lol

I have found out that our machines are capable FOR SURE of bending acrylic(of all kinds) and I am having my guys look into making a smallish tank say, 30gal breeder size.

Most HDPE's are safe, depending on who it is supplied by, and the amount of plasticizers* in the chemical makeup of the material, that can be leached into the water.

And to comment on the Plexiglas, I have a custom top for my 40gal breeder, which has NO support in the middle, and it is slightly sagging. I am betting if I adhered another piece to the bottom of it, to act as a brace, it wouldn't sag at all.


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## ls5292 (Jan 24, 2012)

halffrozen said:


> Odd, it doesn't show that this is MY thread on the index... but ok.. lol
> 
> I have found out that our machines are capable FOR SURE of bending acrylic(of all kinds) and I am having my guys look into making a smallish tank say, 30gal breeder size.
> 
> ...


What thickness of plexiglas?


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## halffrozen (Sep 24, 2011)

1/4"

Though technically is is 0.2"


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