What's the difference in acrylic for my sump or tank?

Plastics – What’s the difference?

You’re looking for a custom sump or to make your own DIY sump or tank.  There’s a term you keep seeing “cell cast acrylic”.  What does that mean?

Extruded vs cast

Extruded/cast acrylic refers to the fabrication method of the acrylic.  Extruded acrylic is squeezed through a form like frosting a cake whereas cast acrylic is poured into a form.  Due to the fabrication method extruded acrylic is more pliable and “softer”.  When it comes to aquarium products extruded acrylic should be avoided as it does not have the strength to hold up to pressure vessels. i.e. aquariums and sumps.

Cast acrylic is the only type of acrylic that should be used for tanks and sumps.  Does that mean any cast acrylic will work?  Not exactly.


Domestic vs imported

We know we need cast acrylic, does that mean we can just get any cast acrylic. 


As we talked about above cast acrylic is the means in which the acrylic is created.  However, it does not refer to the makeup of the acrylic itself.  Staying on food examples, we make something in a round cake pan.  That doesn’t tell us if we made a chocolate cake, vanilla cake, or maybe we got crazy and made a shepherd pie.  

So what does this have to do with imported vs domestic acrylic?  Imported acrylic is always cheaper, but that difference in value has to come from somewhere and in this case the reduced cost is made up in the composition of the acrylic and the quality control.  Even if the acrylic is cast the makeup of the acrylic is still inferior.  Imported acrylic (Chinese and South American in this case) will be more inconsistent and act more like extruded acrylic than cast.

It has the second issue of imported acrylic is being metric.  ¼” imported acrylic is actually 5-6 mm which is almost 20% thinner than its domestic counterparts.  So just by buying imported acrylic you are getting up to 20% less product.

At Building An Obsession we only use domestic cell cast acrylic in our custom sumps and other aquarium products.  We use this for the quality of the material, consistency from sheet to sheet, and because we firmly believe in supporting jobs and the economy of the great nation we live in.


In the end those looking to do some DIY often want to just cut to the chase and ask me what they should buy.  Here are my top brands to look for and to avoid.

#1 Polyone (formerly known as Spartech) Polycast GP

For BAO sumps and products is our go to brand.  It’s a domestically made high quality cell cast acrylic.  Granted the cost is about 40% more than its imported counter parts but we feel the quality is well worth the price.


#2 Arkema PlexiG

This is a great product with both imported and domestic versions.  The domestic version is hard to find but well worth is when you can.  We only use the domestic version when necessary.  There is also a generic version of this which is not the same product.


#3 Reynolds R – Cast

Another great cell cast acrylic.  Only reason it is #3 is because it is really only used when the thickness needed is over 1”.  This is really only used for huge displays and public aquariums


The bad list

#1 Acrystar

This South American acrylic is flat out the worst acrylic we have ever seen.  It’s soft, gummy, and just plain terrible.  To make matters worse acrylic suppliers love to push this stuff due to super high margins.  They’ll make up any story to try and sell it, but avoid it at all costs.

#2 Trucast

We’ve found this material to be thin and extremely inconsistent.  We have tried to use this material for signage in the past and found up to 25% variances in thickness as well as strange particles imbedded in the material.

#3 Chemcast

Chemcast in the late 90’s to early 2000’s was a great brand with some quality material.  However, they moved the plants to China and it has been on fabricators do not use list ever since.  The material completely changed after that so be aware that some might remember the good ole days when I was still usable when referring to its usability. Acrylite followed the exact same history.  Was great in the past when it was made in the USA, but the current Chinese equivalent is not the same.

#4 Unmarked brands

This should be #1 but since there’s no real way to tell what it is we put it at 4.  Any unmarked brand in a paper or plastic masking should be avoided.  Generic is certainly not good in acrylic fabrication where knowing the material and characteristics are so important.  Suppliers will push this stuff hard so just say no.  (side bar:  there are times that brands will mask their sheets in plain paper.  We ordered a custom run of 80 sheets of a color from Polyone once and received it plain masked.  Since we knew it came straight from the factory we were ok with it.  In all other scenarios reject the sheet and get a branded one)



Ask your custom sump builder what material they use.  Look at pictures and verify if possible that they are using the best material for your aquarium project. 



If you are planning on DIY for a project start with the best material and go from there.  If you skimp on the material you will be starting the project at a disadvantage.