Smaller in clear water is the general rule. Its not concrete though. Get alot of colors and sizes. Sandshrimp, coonstripes, eggs and tuna balls all work well when plunking with a spin n glo. Make sure you have a bead chain on your leader or they can twist up to your line. If your crafty you can run multiple rigs on 1 line and cover more water. Use 3-way swivels and separate them by a couple of feet atleast. Good luck!