Acrylic vs Glass the facts

[phixer]

I hope you find this helpful, it seems like this topic has come up pretty frequently lately. Still prefer #4 to 40 though.
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* * * Please do not post links to other websites * * *

 

[turningtim]

Hey Phixer, just thought of a question. As far as the acrylic he recommends is this based on strength, adhesion and clarity? I was just wondering if you could get the high end cast for the front panel and use the extruded for the rest. Kinda like using starfire glass for the front panel etc.......
You got me thinking about this! So when my wife asks what the ---- I'm doing!
Its all you bud!

Tim

 

[phixer]

Hi Tim, hope your Wife has a sense of humor
Extruded has a lower molecular weight and absorbs solvent cements faster than cast or cell cast acrylic. Solvent cementing the two can result in joint failures and crazing due to different material expansion and penetration rates of the solvent between them. Extruded tends to store more internal tension (used to work with a guy like this) :hilarious due to the way its manufactured, frequently rolled or squeezed into shape. (its also more uniform in thickness).
When the two materials become liquid in the solvent medium and weld together the difference is undetectable until the solvent starts to evaporate. Because of the different expansion rates between them, internal stresses within the joint can occur. This tension can stress the joint and induce a failure or cause crazing. It may not even be visible until the tank is filled and under pressure.
Unless annealed, acrylic tanks should be seasoned for several months by sitting empty before filling with water. This it to allow the material time to relax before the pressure/tension of water is applied. This process is for cast acrylic.
You could bond the two with #40 if the machining is good but IMO the weld would not be as strong as one produced by using #4 with the same type of material. I would recommend using straight cast or cell cast acrylic. Ive seen extruded used for skimmers though. You could practice by making a couple smaller QT tanks, and since your a good woodworker many of the same skills will transfer over, especially with a router.

 

[turningtim]

Trust me after almost 20 years shes used to my new hobbies and trail and error phases :scared: !

!
It really does sound like acrylic is very similar to wood in the sense of matching correctly the materials used. And I totally understand the expansion and contraction of material and the bonding effect. I.E. cabinet doors, ply and the use of hardwoods. But in wood I can counter act this by certain types of joinery and allowing it to move. But of course it doesn't hold WATER! I am assuming that crazing is a similar effect as checking when one material moves and the other will not alllow it thus the materail cracks or stresses. correct?
So the bottom line is pick one and stick with it! I think I'm with you on the solvent weld vs an epoxy that bonds the materail. But maybe a little extended disscussion is needed.
Now you've gone and gotten me in trouble.

!
Just something else to feed my brain and most of the time I just do things b/c people say I can't. Just like, "you can't cut 1/2" glass" well guess what.............. ***)
Tim

 

[phixer]

:hilarious thats funny, Im the same way. Well sometimes its better to beg for forgiveness than ask for permission. :hilarious

 

[robchuck]

That article was well written, but seemed to convey the benefits of using an acrylic tank rather than objectively demonstrating the differences between the materials (i.e. "Acrylic vs Glass: The Facts").
For what it's worth, I have a large acrylic reef and would choose acrylic over glass any day of the week, but there are things that I've discovered in keeping this tank where a glass tank would be advantageous. For instance, coralline algae grows very rapidly in my tank (with alkalinity and calcium near NSW levels), and causes me to spend several hours scrubbing the stuff each week while going through countless Kent acrylic scraper blades.

 

[phixer]

This may sound stupid but could the increased coraline algae growth in your acrylic tank be related to the acrylics ability to transmit light better than glass. I mean I dont understand how acrylic would foster the growth of coraline algae more than a glass tank would. Probably just more noticible because of the PITA it can be to remove from acrylic.

 

[robchuck]

I'm not sure why it grows so quickly on acrylic, but I have heard that coralline algae tends to grow much faster on plastics than glass. It's all anecdotal evidence, but if I don't run my cleaning magnet for a week or so, the entire tank gets completely covered in coralline. I've kept reefs in glass tanks before with similar water conditions and only experienced this rate of growth on plastics (powerheads, overflows, etc.). Despite some of the negative attributes that come along with acrylic reef tanks, the piece of mind of having a tough as nails aquarium easily overcomes all of those negatives.

 

[turningtim]

I'm with you there Rob, Thats the only thing that I REALLY don't like. With my glass tank I can scrap to my hearts content with the SS blade in the scraper w/o worry. And yes the coraline does grow very well on PVC and the plastic on the heads. So I guess it may have more of a "tooth" with plastics.
But if thats the only down side , that I have to keep on top of it rather then let it go.........
My wife will be over joy'd! More time spent on the tank!
Tim

 

[turningtim]

Phixer you around? I need that site for someone in New hobbists. Let me know and I'll post my email.

 

[phixer]

MODS, could you please school me up on what types of links are prohibited. Id like to read that particular rule to make sure Im not posting any links in the future that are prohibited. Wasnt able to find any clairification on what types of links were not authorized. As always Thanks for your help.
Tim, I'll have to check out what the rules say again before I can post it. If you want you can email me at phixer@mail.com and I'll send it to ya.

 

[turningtim]

Thanks Phix I send ya mail. Check out New hobbists, someones over there thing of a fairly large tank and I'm sure you would have some input
Thanks Again! Get your email outta here!
Tim

 

[phixer]

Cool, thanks.

 

[shaido]

I guess ill have to figure out which tank to pick based on what info i have.the contiousous marine aquarist says to go with an acrylic tank for thermal,strength,and becuase it holds value.the lfs seems like a good store the stock look good and he swears by glass.I guess ill juast have to think some more.

 

[phixer]

The reason Coraline algae growth is more prevelant on acrylic is because if the acrylic has any scratches the algae will grow inside the scratches, after the algae is scraped a portion of it still remains inside the scratch and grows back quickly. Because acrylic scratches easier than glass this is why the algae is more noticible.
At least thats what they told me today at Scripps when I asked.

 

[cgrant]

Only thing I know is a friend of mine has a 300 gallon acrylic and after seeing what his looks like with age (~ 3 years) I made sure I purchased a glass 210, His acrylic 300 has a ton of small scratches from cleaning, algae, etc.
I am not sure why or if that is normal or not? But after seeing his I made sure to purchase a glass tank.

 

[phixer]

Acrylic requires special handling and maintenance, if its treated like glass that will almost always happen. Have seen acryic public aquariums 15 years old looking great. Its all in how the tank is maintained.

 

[sula]

Phixer,
is there an acrylic polish you can use on the inside of your (empty) acrylic tank and still be reef safe?

 

[phixer]

Ive always used a Micromesh kit to remove scratches on aircraft canopies and aquariums, the polish was a milky stuff but I cant remember who made it. It had the consistency and look of condensed milk.
Novus makes good polish that is non toxic and is safe for use on the inside of the tank. I use a clean cotton diaper or cheese cloth for buffing by hand and then clean with damp warm water using very light pressure to remove any residue.
No more scratches :joy: