Large artificial body of water affected by bacteria and microalgae and system for treating and maintaining it at low cost, comprising: - at least one containing means having a volume of at least 15.000 m 3 for storing water having a temperature of up to 45°C so as to form said artificial large body of water, comprising a receiving means fixed to the bottom surface of the containing means and wherein the receiving means covering the bottom of the containing means is constructed of a non-porous material capable of being cleaned and wherein the non-porous material is selected from a membrane, geo-membrane, geotextile membrane, concrete, coated concrete, plastic liner, or a combination thereof allowing a non-intrusive mobile suction means to travel across the entire surface of the containing means and suction settled particles; - at least one feeding line feeding affluent water to the at least one containing means; - at least one chemical application means; - at least one non-intrusive mobile suction means wherein the mobile suction means is configured to perform a thorough surface cleaning of the receiving means on the bottom surface of the containing means by moving along the bottom of said at least one containing means and suctioning water containing settled particles; - at least one propelling means for moving at least one non-intrusive mobile suction means along the bottom of said at least one containing means; - at least one coupling means that connects said at least one propelling means to said at least one suction means; - at least one filtration means for filtering said water containing settled particles suctioned by the non-intrusive mobile suction means; - at least one collecting line coupled between said at least one mobile suction means and said at least one filtration means; - at least one return line from said at least one filtration means to said at least one containing means; and - at least one coordination means comprising electronic devices wherein the coordination means is configured to receive information regarding water quality parameters, process that information and timely activate processes necessary to adjust parameters of the water within predetermined limits, wherein said processes include the timely activation of the mobile suction means to prevent the thickness of the settled particles from exceeding 3 mm in average, which will simultaneously activate the filtration means so that the system is configured to filter only a small fraction of the entire volume of water of said large artificial body of water, and wherein such processes further include the timely activation of the chemical application means to apply disinfectant agents to the water to maintain an ORP level of at least 500 mV only for a minimum period of time determined according to the water temperature, wherein the minimum period of time is determined according to the water temperature and is 1 hour per 7 days for each °C of water temperature; wherein the system is configured to treat said water so that the water is suitable for low density recreational use. - at least one containing means having a volume of at least 15.000 m 3 for storing water having a temperature of up to 45°C so as to form said artificial large body of water, comprising a receiving means fixed to the bottom surface of the containing means and wherein the receiving means covering the bottom of the containing means is constructed of a non-porous material capable of being cleaned and wherein the non-porous material is selected from a membrane, geo-membrane, geotextile membrane, concrete, coated concrete, plastic liner, or a combination thereof allowing a non-intrusive mobile suction means to travel across the entire surface of the containing means and suction settled particles; - at least one feeding line feeding affluent water to the at least one containing means; - at least one chemical application means; - at least one non-intrusive mobile suction means wherein the mobile suction means is configured to perform a thorough surface cleaning of the receiving means on the bottom surface of the containing means by moving along the bottom of said at least one containing means and suctioning water containing settled particles; - at least one propelling means for moving at least one non-intrusive mobile suction means along the bottom of said at least one containing means; - at least one coupling means that connects said at least one propelling means to said at least one suction means; - at least one filtration means for filtering said water containing settled particles suctioned by the non-intrusive mobile suction means; - at least one collecting line coupled between said at least one mobile suction means and said at least one filtration means; - at least one return line from said at least one filtration means to said at least one containing means; and - at least one coordination means comprising electronic devices