When I started considering a large tank I had been keeping fish for about ten years. The biggest tank I had was a 60 gallon show tank, acrylic, made by TruVu. I knew from experience that acrylic did not haze or become brittle as it was rumored to do, (usually by uninformed people with glass tanks who have a vested interest in convincing themselves acrylic is a poor choice). Nor did it visually bow. In fact after ten years of continual service I was constantly taken by how clear and beautiful it made the water and fish look. (I also had smaller glass tanks.)
That said, a large tank was a substantial investment and I wanted all the facts. When I bought the 60 gallon in 1990 I was fairly new to the hobby and got it because the salesman said acrylic was better than glass. When he got as far as, "it only weighs half as much," I asked where to sign. I could transport it home by myself.
That said, for all I knew I would have been just as happy with a glass tank. If acrylic was better, I wanted to know why - if the only advantage was weight, I might decide to save myself some money and get glass.
To this end I did several months of research, reading innumerable sites, many of
which were acrylic manufacturers - not of tanks - but of acrylic itself. I learned there were different kinds of acrylic (you'll see as you read on), and much of the information I found put many common myths to rest. For example acrylic was used to make the cockpit 'bubble-tops' of fighter planes in WWII, which are "as clear today as they were 50 years ago" even though they have spent countless hours in the sun. I also learned scratches can be removed from acrylic (much more on this as you read on), unlike scratches from glass.
I found that many things which used to be made from glass are now being made from acrylic because it is safer and more durable. Two examples are shower doors and bath enclosures. Acrylic is highly impact resistant and does not "shatter" like glass, even when it finally fails. A force that would shatter glass, may only dent acrylic. (No one wants a dented aquarium but it beats the heck out of a shattered one.) All things being equal, acrylic requires a far greater force than glass before it will crack, break or otherwise fail. If you're talking about a big aquarium, this is obviously a huge plus. While a 20 gallon tank rarely gets in the way, it is common to accidentally whack the front, side, or corner of a big tank. (Note that the corners of acrylic tanks are much less prone to chipping than glass!) Airplane and submarine windows are also made from acrylic. For all its clarity, it's very tough stuff.
I emailed independent acrylic specialists to ask what would be the best brand(s) to use in the application of a large aquarium, and what thickness would be required, and cross-referenced both factors with specs from several aquarium manufacturers. I asked about the different bonding products and how seams are molecularly welded. I also read several sites within the aquarium industry and other sites which had information - some accurate, some not - on the choice.
To be brief (too late!), after several months of research acrylic won, hands down, for many reasons which far outweigh its one drawback - that it can be scratched - and buffed back out. Swim To Top
acrylic is 17x stronger than glass, softer than glass, and more flexible than glass, making it far more impact resistant and not nearly as prone to chip or crack as glass
acrylic weighs 50% less than glass making it far more manageable to move
acrylic insulates 20% better than glass reducing temperature flux, and saving on heating bills
acrylic has molecularly welded, clear polished seams that literally make the tank one solid piece of material unable to leak and therefore guaranteed a lifetime against defects of workmanship
acrylic is as clear as optical glass (at 93% transparency it passes the most light of any material) providing a noticeable difference, especially in larger tanks where normal aquarium glass adds a green tint - acrylic tanks remain crystal clear
Any single one of these facts on its own is impressive, but taken together they make acrylic an unbeatable choice - especially for larger tanks. Virtually all modern public aquariums use acrylic for their tanks, including Aquarium Of The Pacific, located in Long Beach, California, and the Monterey Bay Aquarium in Northern California. Swim To Top
The short answer is that well made tanks - tanks made of the best acrylic of the proper thickness (including the top) - do not bow, though there is mathematically a very small degree of bowing going on. The flexibility of acrylic is what makes it impact resistant. However, a tank made too thin could have some visual bowing. The rule is to make sure the tank you are getting is the proper thickness for it's dimensions (not volume, but dimensions), and make sure the top is as thick as the sides and bottom. Follow these rules and you will be hard-pressed to see any bow.
(Note: Acrylic tanks have solid tops with cut-outs for access, heaters and filters. The solid top provides support to the walls. Some tanks have thick enough walls but the top is made slightly thinner - some manufacturers do this to save money. The top doesn't technically need to be quite as thick as the walls to keep the structural integrity, but thinner tops may warp some, and may allow a slightly noticeable bow to the sides since the top is what gives strength to the sides.)
As for distortion, nothing is clearer than cell cast acrylic. It transmits more light than any other material and can be fashioned into literally any shape, including a bow-front! :). Swim To Top
Acrylic can scratch easier than glass, but scratches can also be removed from
acrylic easily, unlike scratches in glass. Furthermore, underwater scratches are
normally undetectable on acrylic until you drain the tank and discover them. (They can be made by cleaning with tools that aren't specifically for acrylic.) Aside from being able to avoid that, you can easily remove underwater scratches with a scratch removal kit, without harm to your fish or plants, and without draining the tank.
"Acrylic and scratching" is such a hot topic that I have dedicated an entire page to it with some useful links, laying some myths to rest and providing what I hope is helpful 'bottom line' information.
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Yes. There are cheaper grades of acrylic, namely "extruded" or "continuous cast". These grades may be perfectly fine for some applications, but they are not a good choice for an aquarium. Reputable aquarium manufacturers use the best acrylic, domestic cell cast. This acrylic is optically clearer than the others, and harder, making it more scratch-resistant. If you get an acrylic aquarium be sure it is domestic cell cast. Cell cast acrylic also forms an excellent molecular weld. Welded seams are highly polished and transparent. They are made by applying a clear cement ("Weld-On") which interacts with the acrylic on a molecular level, causing a chain reaction that results in the two pieces of acrylic actually "melting" into each other to form one solid piece. Welded seams come with a lifetime guarantee because they can't leak. Ever. Swim To Top
Polycast®, Rohm & Haas®, Cyro Acrylite® and Lucite® are four of the most popular. From the information I gathered from various independent sources within the acrylic and aquarium industries, Polycast is considered to be arguably the best brand, but all of the brands above are domestic cell cast acrylic, and all would make a beautiful aquarium. Swim To Top
There are plenty of manufacturers of acrylic tanks. I chose Advance Aqua Tanks® Clear-for-LifeTM
for a variety of reasons and have been extremely happy. One of the things I really liked about this company was that they responded to my email inquires promptly and courteously. They were one of the few manufacturers to use Polycast (among other top brands) and allow the customer to request a specific brand of acrylic; and of course they make their tanks to the standard thickness, top and walls. I requested Polycast so they made the tank for me, then delivered it to the reseller early, and with the protective masking still stuck to it so I could see they did in fact use Polycast. All this and still [their local reseller/outlet] had one of the most reasonable prices. Their tanks carry a lifetime warranty. (They will also custom build you a tank at a very reasonable price if you want unusual dimensions.)
Another manufacturer is
SeaClear. Though I haven't done business with them they seemed reputable and reasonably priced, and they use top-rated domestic cell cast acrylic, though they did not use Polycast specifically, and I don't believe you can request the brand you want.
I checked out many manufacturers but I am not listing them because some were ridiculously high in price while others skimped on the thickness of their tanks or made the tops thinner than the walls. When I was looking for manufacturers I looked for companies that built their tanks to the generally accepted standard thickness, top and walls, at a reasonable price, using the best acrylic and weld, with a lifetime guarantee. Clear-for-Life was my #1 choice, and SeaClear would have been by #2 choice (only because they didn't offer Polycast).
NOTE: These links are starting points for you to do your own research. Email the company you decide to go with, ask the questions you need to ask, even if it is one of the companies above. Then make your own decisions. As always, management, policies or company standards may have changed since I did my research and bought my tank in early 2001, so don't rely on my word or experience alone. Swim To Top
First of all, don't rely on the local fish store to know what kind of acrylic the tanks they carry are made from, much less the brand of acrylic used. One can't tell from looking, so unless they have specifically asked the manufacturer, they'd have no way of knowing. And even if they claim to know, it's better to get the information yourself from the manufacturer so you can be sure it's accurate. Therefore visit a few local fish stores, jot down the names of the manufacturers (usually there is a manufacturer's decal on the tank), look them up online, and email them. In the email make sure to tell them what size tank you are interested in, along with the dimensions. Ask:
Do you use domestic cell cast acrylic for all your tanks?
What brand is it? (e.g. Polycast, Rohm & Haas...)
How thick is the tank I am interested in?
How thick is the top?
Which cement do you use to weld the seams?
What kind of guarantee comes with the tank?
ANSWERS SHOULD BE...
1. Yes, (we use domestic cell cast on all of our tanks).
2. Polycast, Rohm & Haas, Cyro Acrylite, or Lucite are all excellent, but this is not an exhaustive list. If they name some other brand, look it up online and your search will probably lead you to an acrylic dealer. Email the acrylic dealer, let him know you are buying an acrylic aquarium, and ask how "Brand X" compares to Polycast or Rohm & Haas. They know acrylics, have no stake in the matter, and are usually happy to share their expertise.
Tanks made thicker than the general standard will be more expensive and heavier than they need to be, where most of us are concerned anyway. The only advantages to more thickness would be holding temperature even better than the standard already does, (e.g. if the tank will be going into an unheated garage in North Dakota and you want to save on heating bills, you might consider an extra-thick tank); and being able to sustain even higher impact than the standard already does, (e.g. if the tank is going into a bar room or some other public place where the odds of accidents are much higher and less predictable). In other words there's nothing wrong with a thicker tank but in most cases it's a waste of money and weight. My 240 gallon tank is the standard thickness for its dimensions and is in an unheated garage in CA where the coldest it gets is around 30F in Winter cold snaps. Two 200watt heaters are holding the temp at 74 [where they're set] without any problem. That shows you just how well acrylic insulates, even at the standard thickness. A 240 gallon glass tank calls for ~800 watts of heat, and that's assuming it will be inside in a heated room.
If you go slightly thinner than the general standard, the tank could have some visual bowing and you'll be getting skimped on the other advantages of acrylic - the ability to hold temperature and impact resistance will both be diminished proportionately as thickness is reduced.
In conclusion, the general standard [for thickness] is "just right" for most aquarium applications.
4. Top should be the same thickness as the walls and bottom. A slightly thinner top won't jeopardize the structural integrity but it might allow for some slight visual bowing over time.
5. Weld-On #40 is best (a two-part cement that provides a superior weld which surpasses the needs of an aquarium application). Weld-On #42 is the same product with a different applicator. Weld-On #16 is acceptable (a one part cement that is plenty sufficient for all aquarium applications). Both provide molecularly welded seams and lifetime guarantees by all reputable manufacturers.
6. The tank should come with a lifetime guarantee against workmanship defects. Seams should be guaranteed for life. Swim To Top
If you're looking for a small 10 or 20 gallon tank, glass is fine. It's cheaper and in that size the weight and other factors aren't big issues. However if you're looking to get a nice sized aquarium, do yourself a favor and consider acrylic.
If you want to find more out about acrylic, here's a link to more than you'll ever want to know about plastics: San Diego Plastics, Inc. They also have some great pages for anyone brave enough to build their own acrylic tank, including pictures of huge tanks in various stages of completion.
For a comprehensive but brief FAQ on the history of plastics,
the different manufacturing processes, physical properties, care, etc., click here.
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And finally, here's a couple of newsgroup messages, quoted, that might be of interest. The first was snipped for brevity down to this single paragraph:
I've also seen (as a demonstration) a full 90 gallon tank smacked with a
hammer dead center... maybe not as hard as the guy could have hit it, but he
didnt hold back very much, it distorted the hell out of the front of the tank
right where the head of the hammer hit, but didnt hurt its capacity to hold
water. This was an acrylic tank manufacturer's salesman demonstrating the the
ability of acrylic tanks to withstand impacts to the glass tank manufacturer i
worked for at the time (just to be clear)
asimov@efnet
asimov@starlink
And 4 years before that message was posted…
From: Richard Sexton (richard@news.happy.net)
Newsgroups: alt.aquaria
Date: 1997/06/15
In article <33a3df89.9517623@news.slip.net>, Eric O wrote:
>How can you tell the difference between acrylic and glass?
Hit it with a hammer, hard. If it breaks, it was glass.
Cell cast acrylic that is just 1.25" thick is bullet-resistant. That about says it all. :)
Why I Did This Research & How
