An apparatus for controlling a fluid flow in, into or out of a well, the apparatus comprising: - a main flow channel having an inlet and an outlet being in fluid communication with the fluid flow; - at least one chamber forming part of, or connected in fluid communication with, the main flow channel, the chamber configured for housing at least one flow control element movable between a first position where the flow control element does not block the fluid flow between the inlet and the outlet of the main flow channel, and a second position within or outside of the chamber wherein the flow control element blocks the fluid flow between the inlet and the outlet of the main flow channel, the flow control element movable in response to density of fluid in said chamber, characterised in that: - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel, the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means, so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open. - a main flow channel having an inlet and an outlet being in fluid communication with the fluid flow; - at least one chamber forming part of, or connected in fluid communication with, the main flow channel, the chamber configured for housing at least one flow control element movable between a first position where the flow control element does not block the fluid flow between the inlet and the outlet of the main flow channel, and a second position within or outside of the chamber wherein the flow control element blocks the fluid flow between the inlet and the outlet of the main flow channel, the flow control element movable in response to density of fluid in said chamber, characterised in that: - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel, the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means, so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open. - the main flow channel is provided with pressure changing means comprising an expansion section arranged in the main flow channel, the expansion section having an inlet with a smaller cross sectional flow area than a cross sectional flow area at an outlet, the pressure changing means providing a pressure differential in a fluid return conduit extending between said chamber at a location wherein the flow control element is in the non-blocking position and a portion of the main flow channel being within or upstream of the pressure changing means, so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open.