We have had our pool for 4 years and have had very minimal problems with it up until this year. Our readout on the SWG is reading 700 but when we manually take a reading of the pool we get around 5600 or higher. We have drained the pool about 1/3 of way two times within the past week but the reading still stays the same on the SWG and manual reading. We have had to revert to chlorine tablets in the skimmer and shocking the pool at least every 2 weeks. If we don't the skimmer smells like lake water and fish. You can taste the salt in the pool so I am at a loss. We do have some small black spot( I would assume algae on the bottom of the liner, mainly in the deep end). We replaced the circuit board last year but we are at a loss of what to do next. Thanks