The shock powder might be dichlor or it might be cal-hypo. Look at the label and tell us what the ingredients are. After the trichlor tabs that are currently in the pool dissolve, don't put any more in. You don't want your CYA to get too high. If you are using 10% sodium hypochlorite, then each gallon (4 quarts) will add about 4.5ppm of chlorine.