Mean time in between, work continued on the floor, before the glass fibre is applied as the final coat the pond will be sprayed with expanding polyurethane foam for insulation. I intend to heat in summer to 24c and this insulation will stop a lot of heat being drawn from the pond into the ground. Because of this a little thought was needed with regard to bottom drains, the foam will compress a small amount with the weight of water so I decided to ensure there would be no problem around the bottom drains a little work was needed, also I had to finish the bottom drains 25mm higher than concrete floor level to allow for the foam on the floor.. I made some 550mm x 50mm GRP rings and set these level around each drain, these were then cast in solid concrete. This will allow a firm area for the GRP to terminate.

The final rock was removed in the flat floor area and a former was  made for the perimeter and then the flat base was cast.

The sloping part of the floor was then applied, as can be seen, the thickness of concrete is minimal.

The completed floor. Apart from a small amount of rendering, the pond is now ready for the foam to be sprayed.