You can try going with those keel sinkers that have swivels on either end. To get down 20 feet deep you will have to experiment with speed and lure type. I would go with the 3/4 - 1oz at the very least. You will also want to step up to a baitcasting rod and run a sampo ball bearing swivel on your main line to help cut down on the line twist. I would go with a light action or topwater baitcasting rod to not loose the fish. I use the keel sinkers every now and then and they are ok. The nice thing about them is they catch all the floating debris, weeds ect, on the weight instead of fouling up the lure. Keel weights work best in my opinion, when fishing 30 feet deep or shallower.