An RFG stands for Random Flow Generator. It is a fancy term for a special nozzle that snaps onto loc line and has adaotors to fit onto your existing return pump nozzle. It has a design thst forces water from your return pump in all different directions cresting a very random dispersal of flow. They are an inexpensive way to add movement and flow from your ecisting return pump. I posted a link above to Vivid Aquarium Aquatics who makes the particular models I have. The spiral grille lines force the water in a spiral pattern in all directions.What’s an RFG?