In lined ponds, you must monitor KH or you WILL run out, the pH WILL crash, and you've got a crisis in your pond. Don't bother to test for chlorine or use dechlor. Test your tap water every time you add water to your pond. You never know when you're going to get hit with high doses of chlorine. Always use dechlor.
Chlorine damages the gills - the affects of many small doses of chlorine can add up to major damage.
Assume that your water parameters are fine and don't need to be tested. You need to establish a routine for testing and stick to it. As your pond matures, you can relax your testing routine, but you can't eliminate it. Testing your water is like giving your pond a check-up, do it regularly. At the first sign of trouble, your first response should be to test your water.