The invention relates to a diffusor for adding of gases into water, said diffusor comprising a perforated tube (1) and at least one supply tube (2), said the at least one supply tube (2) is at one end coupled to a source for supplying gas and at the other end in fluid communication with the perforated tube (1), the gas is supplied to the perforated tube (1) through at least one inner supply tube (4; 5; 15) extending from the supply tube (2) to the perforated tube (1). The invention is distinctive in that at the least one inner supply tube (4; 5; 15) is a non-perforating tube and has at least one outlet (4a, 5a, 15a) situated at a free end of the at least one inner supply tube (4, 5, 15), said gas is adapted to be distributed into the perforated tube (1) through the at least one outlet (4a, 5a, 15a).
