i agree with divedog...colour and type would be helpful...
bio load, lighting, feeding habits + water flow and water parameters are needed to asess the situation you have going on..
generally "bandaid treatments" are not a good idea...to simply scrub off the algea may not work or in some cases may not even be a good idea as it may spread the spores faster, giving you a full blow outbreak...especially if the water parameters are ideal for algae growth..
currently i am forgoing an ongoing battle with diatoms, they had completely covered my GSP and now they are gone...i didnt do anything to them..
had some Cyano (red slimey stuff) in the sump upped the flow and now it too is gone..