Duayne makes a good point. In general, 1/2" is good for gizzards but you'll be more prone to gillhangars (i.e. scale loss) if using 1/2" for alewives/threadfin. Use 3/8", even 1/4" depending on size of bait. Also, may want to try a little more salt. 30 gal tank calls for 1 lb rock salt and 1-2 tablespoons bait saver or 4 oz shad saver. The rock salt helps prevent scale loss, so you may want to add a little more.