†† When installing a water garden, is it best to cover the liner with river stones or not?
†† Again, there are two schools of thought in the water garden industry.† One viewpoint is that stones camouflage the liner and create a more natural look.† Stones are said to also enhance biological filtration by hosting the natural bacterial colonies that keep water clear.† This is especially true in a streambed where the water flows through the bed of stones.† Adding aquatics plants to this streambed of gravel or rock creates an effective biological/phytological filtration system.
†† The other side of this coin is that stoning a liner causes a cleaning and maintenance nightmare!† Our experience is that it is impossible to really clean a stoned pond.† Our perspective is that it really is not necessary to camouflage the liner and can actually damage the liner.† First, your plantings will hide the liner.† Then a healthy pond will soon grow a fuzz of filamentous algae.† Even the rocks will soon be indiscernible.
†† To stone or not to stone.† It will come down to personal preference.† It is worth thinking about.† Having water flow through aquatic plants in a gravel bed is excellent for filtration.† This is the basic premise of an external, bio/phyto filter.† Aquatic plants are incredibly prolific and will often overtake whatever they are planted in.† They can eventually interfere with the water flow and will need to be thinned.† What we recommend is not covering the pond liner with stones.† Instead, install an external† bio/phyto filter filled with stone and aquatic plants.† This way, you will have much better control over the cleaning of the rock media and the thinning of the plants.†
†† Another option is to design your pond so the water flows through an upper pool(s) and streambed lined with stone and planted with aquatics.† (Water iris.† Cattails. Water canna.† Almost any type of bog plant.† Aquatic mint and celery.† Iíve even seen lotus growing in such systems.)† To be effective, this areaís surface size should be no less than 10% of the entire pondís surface.† This is really the best of all worlds.† It is definitely something to consider in the design of your pond.