RiverSmallieGuy - That looks like the tank that I designed, except mine was 8'x4'. Basically a screwed together frame with plywood panels and angle supports to stop bowing and bursting. The simple tank is then lined with a sheet of polythene.
For mobility when moving location, the framed panels are easily dismantled as they were all dry screwed. I made the tank in two halves that butt up to each other.
It was a great tank, served me well. In the video below, see the first 15s. To the left of the tank you see cover panels. These prevent algae formation.