Water features in the landscape build up organic materials and detritus over time by biological processes and wind transport. Fish food, sunlight, dust, and whatever else gets into the pond, all add to the load of the pond’s biological system. Materials can remain suspended in the water or settle to the bottom. When materials settle to the bottom they often fill in the gravel with organics leading to decay of these materials and if there are enough present anaerobic conditions at the bottom of the water feature. These processes release chemicals, which usually pushes the ponds natural system out of balance. The typical manifestation is an overabundance of algae or generally cloudy water conditions.
Long story short, we clean the ponds to remove the gunk contributing to an unhealthy system. Some companies will try to vacuum ponds but we have found that, unless you remove most of the water and really work the bottom over, little benefit is gained. Therefore our process is to remove as much of the water as necessary to get the result we are looking for. Sometimes ponds only have a short-term accumulation of leaves and the like and only require small water reduction and a lot of netting to remove the organics. If materials have degraded more it requires more a significant pump down. We put aerators in large tanks to house fish during this process. We then clean the pond, pumps, skimmers, biofilters and anything else that may have build-up in it. Typically we do not use pressure washers, as this shortcut can damage the liner.
After the dirty job is done we refill, dechlorinate the water and run the feature to oxygenate the water. The final step is to equilibrate temperatures and water quality between holding tanks and the pond to avoid shocking the fish at reintroduction. We have yet to link any fish loss to this cleaning system. We also clean fountains and more ornamental water features. This process is more like cleaning a typical pool, with brushes, cleaning agents and pressure washers etc.