Thanks for the helpful replies!
Darn, it sounds like it would just be a whole lot easier to use the potting method. I was really starting to get into the plexi idea. Still, laziness is ever-compelling.
I'd like to keep to glass or plastic, rather than ceramic or stone, at least for this tank. Not sure why, when I think about it... But anyway, preferably plastic, just so it would be lighter. I also want to avoid sharp corners and edges, since both of the goldfish going in this tank are telescopes, and one is completely blind (and the other may be losing her sight, too.)
The tank is 36" long, and I'd prefer something that's ~30" long x ~4-5" wide x ~4-5" deep. Seems that I should make a trip up to the Container Store this weekend! They're
bound to have something close to that.
My plan is to use mostly sturdy, spreading plants (Amazon Sword, Java Fern, Anubias, etc.) to block off the substrate from casual access. However, I learned a trick while using potted plants in my other goldy tank: to use
decorative river stones, turned on their sides, over any bare areas. The stones are too large for the fish to pick up, and their height and close proximity keep the fish from reaching the substrate, so that bare bottom will actually stay bare. The final look is quite nice, as well, especially in clear containers.
I did fiddle a bit with the idea of making a barrier out of sections of glued-together stones that would slot together like puzzle pieces (easier to get in and out of the tank than one huge piece.) But in the end I more-or-less tabled it with the decision that I'm too impatient to get my fishies moved over right now. XD
I may still try the plexi idea, just to see if I can get it to work, but on a smaller scale; maybe a nano to begin with?