Acrylic Question for Sump Build

[Maine_fisher]

Hi Everyone!

I have a couple of questions before I begin a build of a sump for my new aquarium. I am planning a 14" wide by 30" long by 14" tall sump that will have an area of live rock rubble where the water dumps, a large skimmer area, and 4-5 gallon refug.

My questions are as follows:

1. What type of acrlyic should I be using? There seems to be serveral different types. I understand the thickness part, but not the type.

2. Seems like edge prep is one of the most important considerations. Can someone please point me in the right direction?

3. If I can get precision cut pieces of the right stuff I assume this would be better than trying to cut the stuff myself. Is this a correct assumption?

Thanks everyone!

 

[kaipo13]

I was just getting ready to build an acrylic sump as well. Cell cast acrylic is what I understand is needed. The thickness will depend on the dimensions of your sump and your bracing. I am using 3/8" for my sump 61" x 12" x 15" with some bracing and baffles. I think I could have gotten away with 1/4" with all my bracing but why take chances?

The shop I'm getting my acrylic from makes nice cuts so I think I'll be able to get away with just scraping the edges, but if your cuts aren't great you might have to route the edges to get them smooth and straight.

This is my first decent sized acrylic project, I was going to use a tank I had for the sump, but I thought I'd get some acrylic bonding practice in anticipation of building a large acrylic tank later on sometime.

Hope that helps a little, good luck on your project.

 

[Maine_fisher]

Thanks so much...but I was to get a brand name!

 

[kaipo13]

Brand doesn't matter, as long as it's cell cast acrylic, and not extruded.

 

[Jamie9169]

Like kaip13 stated, as long as you use cell cast and not extruded you will be fine. As for prepping the edges, you should get an acrylic scraper, where you get your acrylic will have one, then you just slowly scrape the edges until they are smooth and have no saw marks left on them. It is not a lot of work and it does not take long to do but it is very important to be sure your edges are smooth and uniform. Hope this helps and good luck with your project.

 

[Chris27]

Do you need those exact dimensions? If not, modifying a standard 20L glass aquarium will save you a good bit of money, time and effort...

 

[Acrylics]

brand matters far more than using cast or extruded. If you don't use a good brand, glue joints may not hold at all. All extruded will glue well if you do your part..

Virtually every tank mfr uses Polycast or Plex G, and they are used for very good reason.. I suggest you follow suit

James

 

[kaipo13]

brand matters far more than using cast or extruded. If you don't use a good brand, glue joints may not hold at all. All extruded will glue well if you do your part..

Virtually every tank mfr uses Polycast or Plex G, and they are used for very good reason.. I suggest you follow suit

James

I thought brand wasn't as important as specs? Are you suggesting brand due to quality control or for some other reason? Isn't extruded far less strong than cell cast? I'm a little bit confused about this...

 

[Acrylics]

I thought brand wasn't as important as specs? Are you suggesting brand due to quality control or for some other reason? Isn't extruded far less strong than cell cast? I'm a little bit confused about this...

Most cast acrylics are made to a high molecular weight to reduce crazing (stress.) The problem with this is that we bond acrylic by means of stressing it until it goes into solution, then it cures. If the molecular weight is so high that the material will not go into solution properly - the net effect is that you'll have weak joints. The only 2 brands that consistently make cell cast acrylic that is both glueable and will handle a good bit of stress are Polycast and Plex G.
Acrylite GP, now made off-shore, is questionable at best. IMO their thinner materials (<1") are utter garbage now that they're made in China.

As for extruded, no. Extruded material is just as strong as cast in *every* published physical, optical, and mechanical property. The specs are either exactly the same or similar enough to make any differences negligible. The only real difference between cast and extruded (for our purposes) is molecular chain length (aka molecular weight) which is very low as compared to cast, and not published. What this means is that the material itself cannot handle the stresses (without crazing) that cell cast can, but the molecular chain length is low enough that it will *always* glue well. The issue with this is that it is up to you, the fabricator, to understand that you have to use material thick enough such that it can handle the inherent stresses in the application.

As such, I would recommend people use extruded over a low quality, or inconsistent cast material, but you may have to use a thicker material to alleviate stress. That said, I would *highly* recommend using one of the two brands listed above over extruded.

James

 

[Maine_fisher]

Thanks guys! I thought I saw a long Acrylics thread here? What happened to it?

While I am on the subject of acrylics, I can get my hands on some free cell cast acrylic in black that I want to make my glass tank overflow out of, but the material is only 1/4". I know that I need to have 1/2" for my tank depth, so my question is since my overflow pieces are small (4" x 19") is there so way to weld them to together?

 

[peppie]

Thanks guys! I thought I saw a long Acrylics thread here? What happened to it?

While I am on the subject of acrylics, I can get my hands on some free cell cast acrylic in black that I want to make my glass tank overflow out of, but the material is only 1/4". I know that I need to have 1/2" for my tank depth, so my question is since my overflow pieces are small (4" x 19") is there so way to weld them to together?

I would just use the 1/4''. It will have pressure on both sides once it is in the tank. It will be strong enough without having to weld two pieces together.

 

[kaipo13]

Most cast acrylics are made to a high molecular weight to reduce crazing (stress.) The problem with this is that we bond acrylic by means of stressing it until it goes into solution, then it cures. If the molecular weight is so high that the material will not go into solution properly - the net effect is that you'll have weak joints. The only 2 brands that consistently make cell cast acrylic that is both glueable and will handle a good bit of stress are Polycast and Plex G.
Acrylite GP, now made off-shore, is questionable at best. IMO their thinner materials (<1") are utter garbage now that they're made in China.

As for extruded, no. Extruded material is just as strong as cast in *every* published physical, optical, and mechanical property. The specs are either exactly the same or similar enough to make any differences negligible. The only real difference between cast and extruded (for our purposes) is molecular chain length (aka molecular weight) which is very low as compared to cast, and not published. What this means is that the material itself cannot handle the stresses (without crazing) that cell cast can, but the molecular chain length is low enough that it will *always* glue well. The issue with this is that it is up to you, the fabricator, to understand that you have to use material thick enough such that it can handle the inherent stresses in the application.

As such, I would recommend people use extruded over a low quality, or inconsistent cast material, but you may have to use a thicker material to alleviate stress. That said, I would *highly* recommend using one of the two brands listed above over extruded.

James

Thanks, this helps a lot.

Seeing as I've already ordered the material out of a non preferred brand, I guess this may just be a learning experience. I'll let you know how it goes, and put up a few pics after I finish assembling the sump.

 

[Maine_fisher]

Okay...something I need to know because I've been taking that I can do this for granted. My tank is drilled with a hole in the bottom, but no overflow. I assume that it is an old school tank that used a pipe for an overflow. I been assuming that I could build a overflow out of acrylic and silicone it in place. Will this work????

Thanks!

 

[peppie]

Okay...something I need to know because I've been taking that I can do this for granted. My tank is drilled with a hole in the bottom, but no overflow. I assume that it is an old school tank that used a pipe for an overflow. I been assuming that I could build a overflow out of acrylic and silicone it in place. Will this work????

Thanks!

Sure you can. Many have done it that way. Some types of silicone will work better in this app. than others. Sorry I cant think of the type right off hand.

 

[Maine_fisher]

Sure you can. Many have done it that way. Some types of silicone will work better in this app. than others. Sorry I cant think of the type right off hand.

Hi Peppie...Thanks for the information! Anyone know that right type of silicone to work on glass and acrylic?

Thanks!!

 

[Acrylics]

Hi Peppie...Thanks for the information! Anyone know that right type of silicone to work on glass and acrylic?

Thanks!!

Dow Corning #795 is about the best on acrylic, can't think of anything that works better. GE 1200 series is good too, just not *as* good

James

 

[Maine_fisher]

I assume that these caulks are aquarium safe.

 

[der_wille_zur_macht]

Totally. (Once cured!)

 

[Acrylics]

Just keep in mind that if you use the 795, it is a neutral cure silicone so will take up to 2 weeks to fully cure. The GE 1200 is an acetoxy cure so will cure much faster but would personally give it at least 72 hours of cure time, if not longer.

Both are commonly used in public aquaria and have a long and proven record.

James