Even though payara don't use their teeth to tear through things, I'd be super worried about an accidental shank with one of their teeth through the fabric. When they lose their teeth and a new one comes in, sometimes they don't come in 100% straight and they temporarily stick out of the mouth. It'd only need to happen once and then you've got hundreds of gallons of water on the floor and a dried up armatus.
Definitely not a good tank for them. I'd wait until you find a great deal on something more permanent on craigslist or the like.