How to install preform ponds

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Preformed fibreglass ponds

The alternative to working with a flexible liner is a preform fibreglass pond.

Check carefully before purchase for:

  • Shelf variety and the proportion of deep water to shallow shelf area
  • Choose a shelf layout that does not have a narrow shelf rim around a large expanse of deep water. This is the wrong proportions for a natural looking wildlife pond
  • Always measure your chosen space before going to the Garden Centre. It is easy to be misled looking at an empty pond out of situ.
  • Choose the largest pond your space will allow

Fitting the preform into the ground

  • Often more tricky than you thought
  • Mark out the profile of the pond and its shelves on the ground using a series of hose pipes or string
  • Dig a little larger but as near as possible to the correct shape so that the preform sits snugly in the hole
  • Protect the pond from sharp stones with a layer of geotextile in the hole
  • Bed the pond into the hole so that it is level
  • Start to fill with water and place a spirit level over the top edge
  • As the water starts to weigh down the pond correct the level if necessary while backfilling the space around the preform shape with sand

Preform ponds can work well if placed inside a raised pond surround of concrete blocks

  • Hide the horizontal rim between 2 brick layers
  • Preform ponds have a horizontal rim around the top which is hard /impossible to hide or camouflage into the rest of the garden
  • Water can only fill to just below that rounded top edge or the water will flow away
  • There is no way of creating a vertical upstand as we have recommended with the informal and formal constructions
  • The only way to hide that rim is with slightly overhanging stones or coping slabs dependent on your style of pond