At what point is acrylic 'better' than glass?

[DJKNOX]

This is provably false. The number of threads about bottom seams blowing out on glass tanks far exceed those on acrylic, mostly because the strength of an Acrylic weld far exceeds, by more than an order of magnitude, the strength of silicone and glass. The only acrylic tanks that I've heard blow out a bottom seam were those made with WO40/42 which is an acrylic adhesive with superior strength if done correctly but with horrible strength if done poorly. WO4 will weld with a strength of 2500 psi, your tank will not see even 1/20th that at 36" (16PSI FWIW). Compare that to Dowsil 795, everyone's favorite structural silcone at 45 psi and I think you'll understand why the people who own acrylic continue to own it.

I'm not debating the strength of a proper acrylic weld - but I have read about many large public acrylic aquariums failing without notice. I honestly haven't heard much about glass aquariums "blowing out." I think glass aquariums can have their silicone seals deteriorate over time and thus they spring a leak. Leaks I can manage. If a glass bottom blows out, there was likely something sloppy by the owner - like a faulty stand, undersized glass, a bad scratch caused by dropping rock etc... I can get the safety factor I want on the silicone seals but adding bracing along the bottom seams... and for good measure, the bottom perimeter can be externally braced as well without too much trouble. But agreed, an acrylic weld done properly is a big benefit.

 

[DJKNOX]

Greetings @DJKNOX, I too started this tank as a retirement project. I just jumped the gun a little bit but am now sort of retired thanks to that virus that shall not be named.;Mask I have had glass tanks in the past (up to 220 gallons) and have had no more problems with them than acrylic ones. Meaning I have scratched both. Never had a blown out silicone seam but do know of others who have. Are acrylic tanks easier to scratch than glass? Of course, it's a softer material as we all know. Do they scratch every time you walk by? Well, no, they're not quite that easily scratched. Using the melamine foam cleaner on the mag cleaner also helps keep the inside surface buffed. So in my opinion it's kind of a toss up.
Since I'm running bare bottom I don't have to worry about sand getting caught by the mag cleaner but there is always going to be some kind of calcareous debris to watch out for. I also wanted to drill my own holes for some not so typical plumbing and decided that for me, acrylic would be easier. (Well, that and I got a fairly good deal on the tank too.)
I see (if I'm reading this right) that you are planning on using 2" thick glass. I have no clue as to the stress requirements for how thick the glass should be but that sounds pretty strong. My old 220 glass tank at one point became a planter out in the backyard and when I moved I had to break it up to throw it out. It was only 1" thick and it took some very hard hits with a hammer before it broke! So again, it's a toss up.
The only item I may disagree on is the clarity of acrylic due to thickness. Unlike your assumption of my tank dimensions, (DOH, caught ya ;Playful JK) my tank is a 36" cube with 1.25" thick acrylic. (yes, it's an overkill tank of a tank!) I can look through the side of the front panel through 36" of acrylic and read the writing of this post with ease.
So with all that said I don't know if any of this actually helped or not. Either way, these boxes of water are supposed to be here for our enjoyment, even though they can drive you crazy. (Maybe I should take up golf for "relaxational purposes".;Meh)
Either way you choose to go, can't wait to see your tank get built. Enjoy!

The glass will be 3/4" to 1" whereas the acrylic will need to be 1.5 or 2" depending on the amount of stiffening (euro bracing deployed). As for my assumption on your tank - yup you got me lol. Wasn't expecting a cube!

BTW - I do plan to have a crushed coral and sand bottom in the tank to make the gobies and wrasses happy - so scratching is a heighted risk.

 

[DJKNOX]

@DJKNOX, 1" thick glass. or even Low-Iron at 1" thick. Yup, hard to find if you can. Here is an alternative to think about. Laminated Low-Iron Glass. Two sheets of Low-Iron glass laminated together with a PVB (polyvinyl butyral) interlayer. Looks incredible. Just a thought. We play with a lot of glass options here at Glass Cages.

Thanks Joe. I'm a little skeptical about lamination when it comes to the strength of the combined sheets. My understanding is that if one laminates two 1/2" sheets, the equivalent strength is only about that of 3/4". Its a very technical topic but I've read some technical papers that actually tested the strength of laminated glass under bending load - the performance was less than expected. It kind of makes sense to me, but I certainly don't claim to know what the real science is. Laminated glass does have its other benefits - ie a crack causing failure will effect only 1 sheet. But who wants to take down a 1600 gal aquarium and replace a laminated panel - frightening prospect! I think I would need to go with 2x 5/8" or 2x 3/4" laminated - and then the costs likely exceed the acrylic! It would be all so simple for me if I could get 1" Starphire!

 

[Aardvark1134]

I have never seen a proper acrylic seam bust. Just homemade ones and in their garage builds. There are tons of glass tanks that blow seams out. Just marineland deep deminsion alone has tons and tons of threads on it. Any large glass tank that is not on concrete better be on a metal stand as your floor shifting 1/2 inch is enough to blow out the seam of a large glass tank. Also you have seen the 1000s of red sea threads right? About their larger ones blowing out the bottom seam? It's so bad they now have a reinforment kit for the center of the stand to help stop it from happening. And noone who knows what they are doing would make a huge rimless acrylic tank. The material is not the right type for that. It should be euro braced and likely cross braced for a very large tank. Plus installing glass is a pain in the butt. Here have a video lol

 

[DJKNOX]

I have never seen a proper acrylic seam bust. Just homemade ones and in their garage builds. There are tons of glass tanks that blow seams out. Just marineland deep deminsion alone has tons and tons of threads on it. Any large glass tank that is not on concrete better be on a metal stand as your floor shifting 1/2 inch is enough to blow out the seam of a large glass tank. Also you have seen the 1000s of red sea threads right? About their larger ones blowing out the bottom seam? It's so bad they now have a reinforment kit for the center of the stand to help stop it from happening. And noone who knows what they are doing would make a huge rimless acrylic tank. The material is not the right type for that. It should be euro braced and likely cross braced for a very large tank. Plus installing glass is a pain in the butt. Here have a video lol

Yeah well I'm not gauging this based on mass-produced tanks - as I said, many unsuspecting hobbyists might not appreciate the need for a very stiff stand. I've already designed the stand - maximum deflection is about 1/16 to 1/8" - and yes its metal.

I just googled and found this article. Albeit this is referring to very large aquariums, but you get the idea.

When acrylic aquariums fail

The outstanding properties of PMMA have enabled the construction of massive aquariums, which have become some of the most popular attractions in the world. To prevent sudden, catastrophic failure, however, engineers need to have a thorough understanding of the material’s drawbacks.

www.plasticstoday.com

Aardvark1134 you are one of the strongest advocates for acrylic on this thread - and BTW Louisville's a great town - I've got good friends who live there. But you have not commented on my recent post to @ReeferReboot asking how much work will it be to keep clean and clear 135 ft2 of Acrylic panels on my island aquarium with a sandy bottom - that's a lot of elbow grease to cover 15 square yards of viewing? The MacGyver magnetic polishing idea is nifty, but I really do worry how much I have to treat the acrylic with kid gloves and still work long hours to polish out scratching on so large viewing panes. Could you ball-park the magnitude of effort I could expect?

 

[Aardvark1134]

If you can't afford having someone come clean the sides once a week you can afford a 1600 Gallon reef to start with. The cost of cleaning it would be nothing compared to the cost to build, install, stock, and maintain that thing.

If you want a 1600 gallon glass tank no problem get one...just don't get mad because you can't convice me to get my next tank out of glass because there is no way it will be...not until they get transparent aluminum clearer than just 80% until then cast acrylic for me.

Aluminium oxynitride - Wikipedia

en.wikipedia.org

 

[Cabinetman]

I’d never go glass again. My last acrylic tank was 10’ long and I could clean the front in a few mins with a modified mag float that I welded brackets to that would hold 1/4” thick acrylic blades that were easily removed to sharpen. It would peel any and all coraline in seconds and never did a thing to the acrylic. Scatches are so easy to remove too with a mag float with a sanding kit. Big glass tanks are just scary. The only benefit is that they don’t scratch as easily but if you do get one your stuck with it. I’m building a new 375 soon after a few years off. Wouldn’t dream of going glass.

 

[Joe Glass Cages]

Thanks Joe. I'm a little skeptical about lamination when it comes to the strength of the combined sheets. My understanding is that if one laminates two 1/2" sheets, the equivalent strength is only about that of 3/4". Its a very technical topic but I've read some technical papers that actually tested the strength of laminated glass under bending load - the performance was less than expected. It kind of makes sense to me, but I certainly don't claim to know what the real science is. Laminated glass does have its other benefits - ie a crack causing failure will effect only 1 sheet. But who wants to take down a 1600 gal aquarium and replace a laminated panel - frightening prospect! I think I would need to go with 2x 5/8" or 2x 3/4" laminated - and then the costs likely exceed the acrylic! It would be all so simple for me if I could get 1" Starphire!

True points. Thinking of options. If we all could get 1" glass.

 

[pdxmonkeyboy]

You seem dead set on glass, even when people give you information to the contrary.. acrylic is clearer, the seams are stronger. So just get a glass tank. Just be sure you have a dead flat and STRONG stand.

 

[DJKNOX]

If you can't afford having someone come clean the sides once a week you can afford a 1600 Gallon reef to start with. The cost of cleaning it would be nothing compared to the cost to build, install, stock, and maintain that thing.

If you want a 1600 gallon glass tank no problem get one...just don't get mad because you can't convice me to get my next tank out of glass because there is no way it will be...not until they get transparent aluminum clearer than just 80% until then cast acrylic for me.

Aluminium oxynitride - Wikipedia

en.wikipedia.org

Ah, I wasn't telling you how to buy your next tank. I was looking for good reasons as to why I should buy acrylic. Your solution to a labor intensive design is to pay for cleaning. Great thanks. Did it ever cross your mind that I may not live somewhere where such a service is available?

 

[DJKNOX]

You seem dead set on glass, even when people give you information to the contrary.. acrylic is clearer, the seams are stronger. So just get a glass tank. Just be sure you have a dead flat and STRONG stand.

Actually I am not dead set on glass but rather the arguments for acrylic provided to me are few and not overly convincing. For my situation I don't care about weight or having to relocate the aquarium. If silicone seals were so dangerous, the aquarium hobby wouldn't have been so successful for the past 75 years. Surely those aquariums that HAVE exploded were likely under-designed or poorly-installed in some manner? Clarity of 1.5" acrylic is not better, or at least not noticeably better, than 3/4" low iron glass - because with thickness comes refraction. Acrylic will cost much more than glass and it seems to require much effort to buff. Anyway, I appreciate the experiences being shared. Dude just hire someone to clean and buff out your tank regularly and all will be well. Got it!

But assuming one has to descend and live among us commoners - that is to say, assuming one must service and clean their own monster aquarium - unfortunately none of the acrylic advocates here thus far have directly commented on the effort for this size of aquarium to keep the panes clean and "haze" free? I know with a glass aquarium I will be able to use a windshield squeegee to keep the glass relatively clean without great effort nor much fear of accumulative scratching and ultimately visual degradation. I would really appreciate it the acrylic advocates could contemplate not their own 100 to 300 gal aquariums - which they seem to love - but the size I'm focused on and the consequences of keeping the acrylic in top condition therein.

With a 20 year design life focus, how manageable do you feel 135 ft2 of panes to clean and buff will be at an average age of 70 (60 to 80)? I'm not contemplating glass vs acrylic for a 180 or 280 gal aquarium. BTW, I also love how those 280 gal acrylic aquariums look in the LFS! Give me that for 20 years and I'm all in!

 

[DJKNOX]

I’d never go glass again. My last acrylic tank was 10’ long and I could clean the front in a few mins with a modified mag float that I welded brackets to that would hold 1/4” thick acrylic blades that were easily removed to sharpen. It would peel any and all coraline in seconds and never did a thing to the acrylic. Scatches are so easy to remove too with a mag float with a sanding kit. Big glass tanks are just scary. The only benefit is that they don’t scratch as easily but if you do get one your stuck with it. I’m building a new 375 soon after a few years off. Wouldn’t dream of going glass.

yeah its just that I never scratched a glass tank in all the years I had one. Thanks for your feedback. Sounds like everyone thinks that cleaning and buffing acrylic is a piece of cake...

 

[Antonio Correia]

I currently have a project to build a 170 gallon tank in 15mm thick acrylic. I think primarily of my family's safety. I've seen a glass tank burst. Very dangerous!!!

 

[DJKNOX]

I currently have a project to build a 170 gallon tank in 15mm thick acrylic. I think primarily of my family's safety. I've seen a glass tank burst. Very dangerous!!!

Ola Antonio. You've got my attention. How did that glass tank explode? Do you mean shattered glass? Was the glass tempered ( a big mistake in my opinion ). Curious to hear more!

 

[DHill6]

Glad i'm not the only one who felt this way. I am sure a tank can be sold but it isn't a quick process. I had a miracles starphire 150G tank in my old house. It was gorgeous and well made, not cheap. I listed it on eBay and craigslist. No bites in 30 days, dropped the craigslist price down to $200 and not a single hit. I ended up giving it away to the first person that would pick it up as I needed to get it out for the move.

Same here with a Miracles starfire tank, stand and a sump. Finally $100 took it. Huge loss but it is what it is with used tanks

 

[pdxmonkeyboy]

Says he is not dead set on glass... just ignores or doesn't believe the facts about acrylic. There have been PLENTY of glass tanks that have burst. Especially the bigger ones. But whatever. Have your glass tank built. Its almost as clear and apparently strong enough for your risk level.

 

[tjclapp]

I've noticed a strong preference for glass aquariums around here, and I totally get why. I'm thinkging about upgrading to a much larger setup (73 gal display is a little limiting, no tangs/etc) in a house I'm purchasing and am considering using acrylic for weight reasons. Are the benefits of using acrylic going to be noticeable at the typical size for home aquariums, even 'monster' 1000g systems?

Acrylic is much stronger, and from my understanding cheaper. I have a frag tank made out of acrylic and the only thing I do not like is the scratches.

 

[Squidward]

My 135g standard glass tank was way heavier than my 300g acrylic.

 

[kangadrew]

@DJKNOX, it may help to think of the worst case scenario with each option. With acrylic, you have the potential for a seam to fail IF you go with a shoddy manufacturer. Worst case, if you go a bit too thin, it bows. Acrylic will NOT shatter.

With glass - in time, the silicone deteriorates and tank fails. The amount of time this will take will depend on the quality of the craftsmanship. The other possibility is that before that happens, the pane just shatters without warning.

If I were going purely with glass or acrylic, the above settles it for me. A few options you might like:

• For an acrylic tank (or glass) - you can make an artificial sandbed. Mixing 2-part epoxy and the sand of your choice will let you make something that looks like a real sandbed, but it's hard to the touch. Would let you clean an acrylic tank without scratching it, and give you another plus of being able to keep a "sandbed" with super high flow. If you want a true sandbed for wrasses or other fish, you could do this around the edges and use loose sand in the middle.

• Overall - there are manufacturers that make tanks out of different materials like fiberglass, PVC, and steel. These can let you combine glass (or acrylic) viewing panels with a lightweight, strong frame. Less seals to fail and once you get over roughly an 8' by 4' footprint, it should get cheaper than pure glass or acrylic.

• For cleaning a deep acrylic tank - the King of DIY has a 4 foot deep tank with acrylic windows. Check out this video. Shows some good, cheap ways to clean an acrylic tank.

Few thoughts for you. Ultimately I would strongly advise against glass but hey man, your tank not mine.

 

[DJKNOX]

Says he is not dead set on glass... just ignores or doesn't believe the facts about acrylic. There have been PLENTY of glass tanks that have burst. Especially the bigger ones. But whatever. Have your glass tank built. Its almost as clear and apparently strong enough for your risk level.

I'm not ignoring facts. The fact is that acrylic scratches very easily and I will have 135ft2 of acrylic viewing panels to buff out over 25 years. Yes glass tanks can fail when improperly designed or installed. I haven't heard of large glass tanks failing willy nilly, just myriads of small ones likely for those reasons. Any chance you could point me to threads that analyzed why a glass tank "exploded?" Over on the Monster Tank forum, my poll has more than 75% of respondents preferring a large glass over a large acrylic tank. So it seems I am not alone in my doubts!