Very cool, I love to see the progress here, I just wish I wouldn't have stumbled upon this while at work, I just wasted about 1 hour reading
It may be the camera angle, I don't know, but it looks like the tank has a big twist in it. The back is lower and the top twisted towards the camera so you can see the top. While on the left it is up and twisted to the front...??
early on he mentions industrial formulator's cold cure epoxy. I believe that product stays flexible. it is used as an industrial floor sealant for cold temperatures.