A filter for filtering water for a pump for an aquarium or a pond, which filter comprises a housing (14), at least one inlet in the housing (14), at least one outlet in the housing (14), at least one filter member (18) in the housing, at least one passageway in the housing (14), and at least one water flow control means; the filter member (18) having a body through which water to be filtered passes to the inside of the filter member (18), and a portion at which filtered water inside the filter member (18) is able to pass to the outlet; and the filter being characterized in that the water flow control means comprises at least one bypass inlet for controlling the water flow, the bypass inlet being such that it firstly controls the water flow direction and velocity as the water enters the bypass inlet, it secondly controls that water flow direction and velocity as the water leaves the bypass inlet, and it thirdly controls the water flow that bypasses the inlet; whereby the filter is such that, in use, the water enters the housing from the inlet at a controlled flow rate which does not attract already separated solids, whereby separated solids settle in the housing and filtered water passes through the filter member to the outlet.