Method for treating aqueous feed by dissolved gas flotation, especially by dissolved air flotation, the aqueous feed originating from an industrial processing of fibrous material of cellulosic origin, such as manufacture of pulp, paper, board, recycled fibre pulp or the like, wherein the aqueous feed comprises an aqueous phase and solid particulate material suspended in the aqueous phase, wherein the method comprises - bringing a flocculant in contact with the aqueous feed and flocculating suspended solid particulate material into flocs through interaction of flocculant and suspended solid particulate material, - contacting formed flocs with gas bubbles and inducing their flotation in a flotation basin, characterized in that the flocculant, which is used for flocculating suspended solid particulate material, comprises a polymer composition having a charge density of at the most 1.7 meq/g dry, preferably at the most 1.5 meq/g dry, more preferably at the most 1.1 meq/g dry, the polymer composition comprising - a cationic synthetic first polymer, which has a charge density at least 1.0 meq/g dry at pH 2.8, - at least one cationic second polymer, which is a polymer obtained by polymerisation of (meth)acrylamide and at least one cationic second monomer, the amount of second monomer being 0.2 - 19 weight-%, calculated from the total dry polymeric material weight of the polymer composition, wherein the second polymer is polymerised in the presence of the cationic first polymer, wherein the first polymer has a higher charge density than the second polymer. - bringing a flocculant in contact with the aqueous feed and flocculating suspended solid particulate material into flocs through interaction of flocculant and suspended solid particulate material, - contacting formed flocs with gas bubbles and inducing their flotation in a flotation basin, characterized in that the flocculant, which is used for flocculating suspended solid particulate material, comprises a polymer composition having a charge density of at the most 1.7 meq/g dry, preferably at the most 1.5 meq/g dry, more preferably at the most 1.1 meq/g dry, the polymer composition comprising - a cationic synthetic first polymer, which has a charge density at least 1.0 meq/g dry at pH 2.8, - at least one cationic second polymer, which is a polymer obtained by polymerisation of (meth)acrylamide and at least one cationic second monomer, the amount of second monomer being 0.2 - 19 weight-%, calculated from the total dry polymeric material weight of the polymer composition, wherein the second polymer is polymerised in the presence of the cationic first polymer, - a cationic synthetic first polymer, which has a charge density at least 1.0 meq/g dry at pH 2.8, - at least one cationic second polymer, which is a polymer obtained by polymerisation of (meth)acrylamide and at least one cationic second monomer, the amount of second monomer being 0.2 - 19 weight-%, calculated from the total dry polymeric material weight of the polymer composition, wherein the second polymer is polymerised in the presence of the cationic first polymer, wherein the first polymer has a higher charge density than the second polymer.