How to clean aquarium equipment?

Well, in my 20 gallon freshwater aquarium I realized this morning that I have a slight case of brown algae, diatoms right? I have had had this aquarium since late March and cycled it with fish. The brown algae is only on the very top of this large decoration I have, and on the top of this smaller decoration. I have some cleaning equipment, but it's been sitting out for a while and I would like to clean it before I use it on the decorations. So, how do I clean these things without endangering my fish? Thanks in advance!