if you go the way of the kiddie pool, try putting a 1" styrofoam insulation sheet underneath it, then some spray foam from that and all the way to the foam. not only will it insulate but it will also stiffen up the sides a bit. Consider also that you will be looking at the fish from the top, so go for some lighter colored sand(perhaps even white) to pump up the contrast with your fish.
you may want to look up ebay for all sorts of containers and pools. I recently purchased an 8' diameter intex pool for $60 that already comes with a filter that Im going to use just to circulate the water. too big for your application unless you're going to get more/bigger fish. Your pleco might want some more room later on too.
anyways, to each his own! hope to see some pictures of what you decide to do
you may want to look up ebay for all sorts of containers and pools. I recently purchased an 8' diameter intex pool for $60 that already comes with a filter that Im going to use just to circulate the water. too big for your application unless you're going to get more/bigger fish. Your pleco might want some more room later on too.
anyways, to each his own! hope to see some pictures of what you decide to do