Mechanical filters require the entire volume of water in the pond to circulate through them at least once every hour to be effective. These filters are easy to install and generally lay on the bottom of the pond, but may need cleaning as often as once every few days. The biological filters are more expensive but need less care. Biological filters are more difficult to install but may need attention as seldom as once a month. Concrete is basic in nature and will have a detrimental effect on life in the pond.
Plastic is the best material for pots.
Pots for aquatic plants may be pails, buckets, baskets, or pans. Baskets are often the best choice as they allow more surface interface of soil and water for gas exchange. Baskets, however, must be lined with a burlap type material to prevent the soil from clouding the water. This soil should be free from fertilizers, herbicides and other pesticides. These chemicals, if not directly toxic to the plants, can leach out and cause damage to fish and animals living in the pond.