Building a Large Acrylic Tank - Questions and Build Thread

NigeltheBold

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I'm seriously considering building my own 300 gallon rectangular acrylic tank in my basement. I'm thinking of building my own to save a little money, avoid having to squeeze a giant tank down my stairs, and to have a fun project to work on over the next few months. I'd like to keep some bigger marine fish in the tank, maybe a small shark or ray or some larger non-reef safe fish. I have a reef tank, but I've always wanted to have a large format/FOWLR tank as well.

Anyway, since this could be a pretty big undertaking, I know I'll need to gather some knowledge before diving in. I'm pretty handy, I enjoy DIY projects, I have plenty of tools and experience working with wood and other materials, but I've never worked with acrylic (let alone large sheets of acrylic that need to be bonded together). So I thought I'd start with some questions about tank design and construction:

First of all, based on the bit of research that I've done about building an acrylic tank, it looks like the panels are fastened together using Acrylic cement. I see a lot of people using a product called Weld-On 4 to bond the acrylic panels. It looks like once the panels are bonded and the cement is fully cured, people use clear or black silicone to seal the corners. So, first question: does anyone suggest a different product or method to bond the panels?

I've seen some large tank designs with metal bracing on the corners. Some have bracing on all corners, some just on the bottom, some on the bottom and top, but not the vertical edges. I've also see tanks with what's called EuroBracing on the top, which I'd be fine with, but I don't know if I'm able to do it with acrylic since I'm not comfortable making large or rounded cuts (I'd be fine with cutting some strips and small pieces). I'd like to build an 84" x 36" x 30" tank. So this leads to my second set of questions: how do I figure out whether or not I need bracing on the corners? What about EuroBracing on top? Can that be done with strips of acrylic and cement?

And since I could be potentially housing some fish that may want to jump, I'm guessing I'll need some kind of lid. Has anyone had experience building their own lids out of acrylic? Ideally, I'd like something with hinges or slides. I'd rather not just throw a loose sheet of acrylic over the top and call it a lid.

Well, I think this is more than enough to get a discussion going. Once I get some of these questions answered, I'll move on to further design topics such as filtration (overflow & sump location), plumbing, lighting, and eventually a stand to hold this massive thing. I know this is going to be a long process, but I'm interested to learn more and I want to make sure I do it correctly. Thanks in advance for your help and insight!
 
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I'm seriously considering building my own 300 gallon rectangular acrylic tank in my basement. I'm thinking of building my own to save a little money, avoid having to squeeze a giant tank down my stairs, and to have a fun project to work on over the next few months. I'd like to keep some bigger marine fish in the tank, maybe a small shark or ray or some larger non-reef safe fish. I have a reef tank, but I've always wanted to have a large format/FOWLR tank as well.

Anyway, since this could be a pretty big undertaking, I know I'll need to gather some knowledge before diving in. I'm pretty handy, I enjoy DIY projects, I have plenty of tools and experience working with wood and other materials, but I've never worked with acrylic (let alone large sheets of acrylic that need to be bonded together). So I thought I'd start with some questions about tank design and construction:

First of all, based on the bit of research that I've done about building an acrylic tank, it looks like the panels are fastened together using Acrylic cement. I see a lot of people using a product called Weld-On 4 to bond the acrylic panels. It looks like once the panels are bonded and the cement is fully cured, people use clear or black silicone to seal the corners. So, first question: does anyone suggest a different product or method to bond the panels?

I've seen some large tank designs with metal bracing on the corners. Some have bracing on all corners, some just on the bottom, some on the bottom and top, but not the vertical edges. I've also see tanks with what's called EuroBracing on the top, which I'd be fine with, but I don't know if I'm able to do it with acrylic since I'm not comfortable making large or rounded cuts (I'd be fine with cutting some strips and small pieces). I'd like to build an 84" x 36" x 30" tank. So this leads to my second set of questions: how do I figure out whether or not I need bracing on the corners? What about EuroBracing on top? Can that be done with strips of acrylic and cement?

And since I could be potentially housing some fish that may want to jump, I'm guessing I'll need some kind of lid. Has anyone had experience building their own lids out of acrylic? Ideally, I'd like something with hinges or slides. I'd rather not just throw a loose sheet of acrylic over the top and call it a lid.

Well, I think this is more than enough to get a discussion going. Once I get some of these questions answered, I'll move on to further design topics such as filtration (overflow & sump location), plumbing, lighting, and eventually a stand to hold this massive thing. I know this is going to be a long process, but I'm interested to learn more and I want to make sure I do it correctly. Thanks in advance for your help and insight!
there are youtube videos that will answer most of your questions, but the one thing I would recommend is using polycarbonate material, acrylic is a weak material made for smaller tanks, unless you are going really thick.
 
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NigeltheBold

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there are youtube videos that will answer most of your questions, but the one thing I would recommend is using polycarbonate material, acrylic is a weak material made for smaller tanks, unless you are going really thick.
I was planning at least 1/2" acrylic if not 5/8 or 3/4. I guess I didn't know polycarbonate was an option. What thickness would you recommend for polycarbonate?
 
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I was planning at least 1/2" acrylic if not 5/8 or 3/4. I guess I didn't know polycarbonate was an option. What thickness would you recommend for polycarbonate?
Ive seen 300 gallon tanks made with polycarbonate at 5/8" thick, with a one piece top for support with openings for access into the tank for rocks and whatnot.. A client of mine had a custom 300 gallon made out of polycarbonate. The only setback is that it is very expensive.

If you decide to do acrylic material. I would go 1" thick minimum for a 300 gallon tank. but If your going custom,, Why not glass?

in any case, do as much research as you can on solvent glues and what the standards are for the material your working with is for saltwater application.... the only setback is that when you make your own tank, there is no warranty, and can be frustrating. at times... so research is paramount..
 
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NigeltheBold

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Ive seen 300 gallon tanks made with polycarbonate at 5/8" thick, with a one piece top for support with openings for access into the tank for rocks and whatnot.. A client of mine had a custom 300 gallon made out of polycarbonate. The only setback is that it is very expensive.

If you decide to do acrylic material. I would go 1" thick minimum for a 300 gallon tank. but If your going custom,, Why not glass?

in any case, do as much research as you can on solvent glues and what the standards are for the material your working with is for saltwater application.... the only setback is that when you make your own tank, there is no warranty, and can be frustrating. at times... so research is paramount..
Browsing around on Google, I'm seeing lots of places that have 1/2" polycarbonate available for custom sizes, but not 5/8". I also stumbled upon a thread or two that said polycarbonate isn't as clear as acrylic and it yellows over time. Have you noticed that?

1/2" polycarbonate doesn't seem to be too expensive, if I can get away with it. Maybe reducing the height of the tank to 24" would allow me to do that? 1" acrylic is super expensive and it's probably very heavy. Even 3/4" acrylic is expensive.

I don't want to use glass because I have young kids and I don't want to risk breakage/cracks. I want something more durable.
 

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Browsing around on Google, I'm seeing lots of places that have 1/2" polycarbonate available for custom sizes, but not 5/8". I also stumbled upon a thread or two that said polycarbonate isn't as clear as acrylic and it yellows over time. Have you noticed that?

1/2" polycarbonate doesn't seem to be too expensive, if I can get away with it. Maybe reducing the height of the tank to 24" would allow me to do that? 1" acrylic is super expensive and it's probably very heavy. Even 3/4" acrylic is expensive.

I don't want to use glass because I have young kids and I don't want to risk breakage/cracks. I want something more durable.
I totally understand the safety concern you have with using glass. 1/2" should be fine, i think that the yellowing comes from high exposure to UV, just remember, if you are to use acrylic, you would have to go much thicker.

Ill ask my client what the dimensions on his tank is to give you a better idea.
 
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NigeltheBold

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I totally understand the safety concern you have with using glass. 1/2" should be fine, i think that the yellowing comes from high exposure to UV, just remember, if you are to use acrylic, you would have to go much thicker.

Ill ask my client what the dimensions on his tank is to give you a better idea.

Appreciate the help. Sounds like 1/2" Polycarbonate is the plan then. After some quick research, I found a higher-strength solvent cement that is good for super-clear bonds, and it also works on polycarbonate. People have used it for larger acrylic and polycarbonate aquariums and it seems to hold up better than the other solvent cements over time. It's called Weld-On #40, and it's a 2-part cement. I think it can be purchased with the self-mixing nozzle to make application a bit easier. My only concern is that this stuff is a bit thicker than #3 or #4, and I'm not sure how to handle the excess that will inevitably squeeze out of the joints when I glue them together... will it need to be wiped up with something? Or can I just leave it alone? I'll maybe need to contact the manufacturer with that question.

So the next thing I need to figure out is the eurobracing on the top. Can I piece it together using strips of 1/2" polycarbonate? Or does it need to be one piece?

From there, I can come up with a basic lid design and start thinking about my overflow box/boxes.
 

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Appreciate the help. Sounds like 1/2" Polycarbonate is the plan then. After some quick research, I found a higher-strength solvent cement that is good for super-clear bonds, and it also works on polycarbonate. People have used it for larger acrylic and polycarbonate aquariums and it seems to hold up better than the other solvent cements over time. It's called Weld-On #40, and it's a 2-part cement. I think it can be purchased with the self-mixing nozzle to make application a bit easier. My only concern is that this stuff is a bit thicker than #3 or #4, and I'm not sure how to handle the excess that will inevitably squeeze out of the joints when I glue them together... will it need to be wiped up with something? Or can I just leave it alone? I'll maybe need to contact the manufacturer with that question.

So the next thing I need to figure out is the eurobracing on the top. Can I piece it together using strips of 1/2" polycarbonate? Or does it need to be one piece?

From there, I can come up with a basic lid design and start thinking about my overflow box/boxes.
Research is where you will find success, I strongly recommend that you checkout some youtube videos on tank building with poly Carbonate material, you can always mask the exterior and interior corners of the tank if your concerned about the excess glue, or you can use a DIY sized spreader to run it along the corners like its silicone. the secret is to practice on small pieces to avoide bubbles trapped in between the two sheets. as far as the top, I would use one piece, maybe find a local sign shop that has a CNC router that can cut out the interior of the openings, or use a template and use a variable speed router to help you make the cutouts..

I will get you those dimensions on the 300 my client has tomorrow to help you make it right as far as specs on a tank that large.
 

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Plenty of information about acrylic fabrication at @Turbo's Aquatics thread about acrylic fabrication on this forum. I would use cell cast acrylic only in 1" thickness at least for your build. You can mix your own solvent for better water clear bonds. Seam preparation and assembly sequence is very important for a great finish and proper seam strength. Never used polycarbonate due to the higher amount of moisture adsorption and less than clear panels compared to acrylic. Polycarbonate does make good access covers for the tank. It is better to use a solid top sheet with routed out access openings for the best strength in the tank design. Weldon 42 comes in a cartridge and uses a gun and mixing tips but it was only sold to professional fabrication companies not to long ago. Good luck.
 
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NigeltheBold

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Plenty of information about acrylic fabrication at @Turbo's Aquatics thread about acrylic fabrication on this forum. I would use cell cast acrylic only in 1" thickness at least for your build. You can mix your own solvent for better water clear bonds. Seam preparation and assembly sequence is very important for a great finish and proper seam strength. Never used polycarbonate due to the higher amount of moisture adsorption and less than clear panels compared to acrylic. Polycarbonate does make good access covers for the tank. It is better to use a solid top sheet with routed out access openings for the best strength in the tank design. Weldon 42 comes in a cartridge and uses a gun and mixing tips but it was only sold to professional fabrication companies not to long ago. Good luck.

Seems like there's mixed opinions on whether or not to use Polycarbonate to build tanks. Acrylic is definitely more common, but it has to be thicker than polycarbonate, which makes it a LOT more expensive. If I did an 84x36x24 tank out of 1" acrylic, it would cost over $2800 plus shipping, which isn't cheap. And if I went down to 3/4" acrylic, it would cost over $2000 plus shipping. In comparison, using 1/2" polycarbonate would cost around $1800 plus shipping. (none of these options include the top bracing, but I'm assuming that'll add another few hundred dollars depending on the thickness and material).

If I were to choose acrylic, I might as well just buy a pre-built tank like this one. I don't know how thick it is, but it's professionally made, comes with Euro Bracing, and ships for free. It has a warranty against leakage but I don't see anything in the warranty that covers bowing. The other problem is, it would be very tough to get this thing down my basement stairs. I'd have to get it through a 27" wide doorway, then rotate it on it's end and tilt it so it can fit down the staircase without touching the ceiling. Sounds daunting... that's why I was planning on building my own and bringing the sheets down the stairs one by one. When it comes time to remove the tank, I would cut it into smaller sections using a saw.
 

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Not an expert, but I’ve had many acrylic tanks custom built for me… the required thickness is dictated more from the height of the tank than the overall size. If you’re only going to be 24” top to bottom. 1/2” should be fine.
 
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NigeltheBold

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Not an expert, but I’ve had many acrylic tanks custom built for me… the required thickness is dictated more from the height of the tank than the overall size. If you’re only going to be 24” top to bottom. 1/2” should be fine.

Yes, I think reducing the height of the tank to 24" or 26" would allow me to use thinner acrylic. On the first page @Turbo's Aquatics thread, it says that I can get away with 1/2" acrylic on a tank up to 24" tall as long as it has proper Euro Bracing. So I may do that, or I may do a 26-28" tall tank with 3/4" acrylic and Euro Bracing. He says you don't need 1" thick acrylic unless you go up to 36" in height (with Euro Bracing).

So, now that I've got plenty of info (and I've seen plenty of opinions) on material and thickness, I think I'd like to start thinking about filtration and plumbing setup. Here are my thoughts so far:

  • Initially, I was thinking I'd build my own sump, install overflows in the tank, mechanically filter the water as it enters the sump (using a roller mat filter or something), then run it through a refugium, then a skimmer chamber, and back up to the tank. This is what I do on my reef tank and it works very well- so we'll in fact, that I don't do water changes. I monitor nitrate and maintain it around 3-5ppm for the corals. I use the triton method and dose supplements as needed. It's been working well for a couple of years now. Ideally, I want to minimize water changes in this new tank, however, I know there won't be coral to help eat-up nitrates and there will be some larger fish that could potentially cause higher nitrate levels. So, I'm not expecting to get away with zero water changes. Just trying to reduce them by having plenty of de-nitrifying bacteria in the system and macro in the refugium to help consume nitrates.

  • I've done some reading about filtration for large tanks (300+) and I've heard great things about Bead Filters, which are normally used for backyard ponds. Apparently they're mechanical and biological filtration in one, and they never require media replacement or difficult cleaning. They can be backflushed to remove debris, and it sounds pretty easy according to reviews. The only problem is, bead filters are pressure filters and they're meant to be plumbed inline. So this would eliminate the sump from the equation. And I don't know if bead filters provide much denitrification to help reduce nitrates and therefore minimize water changes.

  • So here's my next set of questions: can I somehow have both a sump with refugium AND an inline bead filter? Is it possible to feed the sump with bead-filtered water, or would the sump have to be separate because it's not under pressure? Or, if I'm going to have a sump anyway, should I ditch the bead filter idea and just use a roller mat for mechanical filtration instead?
 
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Don't use polycarbonate. You will be hard pressed to find a solvent that will hold over time polycarbonate. Moreso, the bow on polycarbonate will make your tank like a balloon.
 

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Don't use polycarbonate. You will be hard pressed to find a solvent that will hold over time polycarbonate. Moreso, the bow on polycarbonate will make your tank like a balloon.
 
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NigeltheBold

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Don't use polycarbonate. You will be hard pressed to find a solvent that will hold over time polycarbonate. Moreso, the bow on polycarbonate will make your tank like a balloon.

I'm going to use 3/4" acrylic. Several experienced builders have told me that 3/4" will be fine up to about 28" in tank height.

Still looking for some opinions on filtration though. Anybody have experience with Bead Filters? I'm a little worried that the backflushing process will waste too much water... So maybe a roller fleece filter is the way to go. Thinking I might build my own sump out of a 60 gallon breeder tank and include space for a refugium to help with nitrate reduction.

Any opinions? I could start another thread elsewhere but I thought I'd ask here first.
 
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albano

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I see a lot of people using a product called Weld-On 4 to bond the acrylic panels. It looks like once the panels are bonded and the cement is fully cured, people use clear or black silicone to seal the corners…
Don’t think that I’ve ever seen a professionally built acrylic tank with silicone in the corners!
Sounds like the panels did not bond correctly in the corners and the silicone was used to correct the problem… probably not a good fix!
 
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NigeltheBold

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Don’t think that I’ve ever seen a professionally built acrylic tank with silicone in the corners!
Sounds like the panels did not bond correctly in the corners and the silicone was used to correct the problem… probably not a good fix!

Not really sure what you're referring to... I'm not talking about a professionally built acrylic tank. I'm talking about methods used to bond and seal acrylic when building a tank at home.

Are you saying that I shouldn't need silicone sealant if I use a proper bonding agent? I thought both were necessary, but maybe I'm wrong?
 

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Are you saying that I shouldn't need silicone sealant if I use a proper bonding agent? I thought both were necessary, but maybe I'm wrong?
Exactly… if done correctly, you shouldn’t need silicone, which won’t really bond well to acrylic, anyway.
 
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Not really sure what you're referring to... I'm not talking about a professionally built acrylic tank. I'm talking about methods used to bond and seal acrylic when building a tank at home.

Are you saying that I shouldn't need silicone sealant if I use a proper bonding agent? I thought both were necessary, but maybe I'm wrong?
Typically, one would use weld on 4 for where the panels meet and then weld on 16 to apply to the seam on the inside of the tank as a "just to be sure". Sometimes the weld on 16 is laid out similar to how silicone looks when dry in a standard fish tank.
 
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NigeltheBold

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Typically, one would use weld on 4 for where the panels meet and then weld on 16 to apply to the seam on the inside of the tank as a "just to be sure". Sometimes the weld on 16 is laid out similar to how silicone looks when dry in a standard fish tank.

What about Weld-On #40? I've heard of some people using that instead of #3/#4/#16 because it's a lot stronger.
 

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