We often get requests for rimless tanks in acrylic, and questions about the high price after we provide a quote, so I'll take a second to explain why rimless tanks and acrylic are really not a good combination.
Acrylic does not have nearly the same strength of glass when it comes to bending. So that means a tank made with 3/8" glass will require significantly thicker material in acrylic. Also material thickness increases faster with the height of the tank than the length and with of the tank. This is because the force of the water is much greater as height increases as opposed to length and width.
So what does this mean? Simply put, if you want a rimless aquarium you should probably look to glass rather than acrylic. The exception is frag tanks. Because frag tanks are generally 10" or under either 1/2" or 3/8" cell cast acrylic can sometimes be used to achieve a rimless look. Each manufacturer publishes correct thickness of acrylic depending on use, or their engineering department is available to validate usage. Make sure your builder has access to these resources to ensure that the correct thickness of material is used.
Here at BAO, we fabricate custom tanks, frag tanks, custom sumps, auto top off reservoirs. If you find a need for anything don't hesitate to contact us. Our contact information is available on our Contact Us page. We love talking with the reefing community so feel free to give us a ring.