I purchase my acrylic from Interstate Plastics (Order form at the bottom of theirweb page)
You can purchase precut acrylic at affordable prices, as well as the adhesives and other tools from them.
You can find precut acrylic sheets under "Materials" and adhesives and tools under "Accessories" in their navigation bar.
They will also cut-to-size acrylic for you.

For breeding and housing my betta's I use the Cut to Size order form and order 1/4" thick, 8" x 36" sheets and 1/4" thick 8" x 7 3/4" sheets. I use a thick adhesive (because I am still new at this and need all the help I can get!)

After all sides of the tank are welded together (and allow to set for 24 hours), I then run silcone/sealant along the joined pieces. I get my silicone at ThatPetPlace.com and use Aquarium Sealant 10.3oz (Perfecto).

At a craft store, Michaels, I purchase blank/plastic needlepoint canvas to use as tank dividers. This allows the water to flow through the tanks and also allows the fish to see each other.

The dividers are placed in the tank by using u-channels that I purchase at www.usplastic.com. The u-channels are set in place with the silicone sealant.

The dividers (needle point canvas) are cut to size and slipped into the u-channel sholder.

There are different size meshes in the needlepoint canvases. I like to use the very fine mesh canvas for raising fry and the largest mesh for dividing adults and allowing males to court females.

 

I will update this soon with more detailed information.