Natural swimming ponds using treatment wetlands (TWs) as an element of treatment of swimming water are an ecologically beneficial alternative to conventional pools. Unlike conventional swimming pools, in natural swimming ponds, the water treatment avoids the use of chemical methods and is based on the phenomenon of water self-purification and the rhizofiltration capacity of repository macrophytes in TWs of the regeneration zone, as well as on typical physical filtering processes (e.g., straining, sedimentation, or flotation), physicochemical filtration (physical and chemical adsorption, mainly of phosphorus), and biological filtration (nitrification and denitrification). Market solutions usually arise from the implementation of water treatment solutions used in small garden ponds, which are not typical for ponds; moreover, they are expensive and difficult to use and maintain. Therefore, they require the development of a dedicated system that improves the functioning and usability of the filtration system. A modular, compact filtration system for the treatment of water by physical and biological methods, made of polymer composites and with replaceable filtration modules and essential equipment (e.g., skimmers, dispensers, and filtration mats), is a solution expected by many pond users. It enables the exploitation of the natural functions of ponds and contributes to the preservation of biodiversity and active recreation in a biologically living aquatic ecosystem.