Thanks to everyone who have responded to my pics and to answer vildotcom's question, my pond is about a metre plus in the ground. It has a seven inch reinforced concrete slab base and the main shape is constructed in bricks and mortar. It was cement rendered and then completely fibreglassed. Final stage was to concrete with pilbara ironstone the entire inside walls and top edges.(millions of hiding places for the bristlenose, cichlids and yabbies). i built in several rock ledge caves and put about three inches of heavy gravel in the bottom. There is also a colony of about twelve clown loaches that we see a lot of in the summer,who love the rocky caves.Some of the rocks under the waterfall area and in different parts of the landscaping weigh three to four hundred kilos. there is probally about fifteen ton of rocks all up....Thanks for your interest.