A visual display panel (1) comprising: a front face (3); an array of optical display elements, a plurality of fluid flow conduits, each conduit extending through the panel from an aperture on the front face; and a manifold (32) in fluid communication with one or more of the plurality of fluid flow conduits, the manifold having one or more manifold inlets (38) fluidly coupled to a fluid pump (33) for displacing fluid through the conduits.