The bio pellet instructions tell you how much to use. Usually amount/10gal of water. Just use half that for two weeks. And soak the beads in rodi
water overnight. What brand bio pellet you go with?
And with the two little fishes you will need a slight modification for bio pellets. Go to a fabric/craft store and get yourself a package of plastic circle knitting wheels. They look like round plastic screens. Should only be a couple dollars for a package. You will cut the middle out of two of these so they slip over the center tube if the reactor. Put one above each diffuser plate in the reactor.