30 year fish enthusiast. Well water. In the last yr have been loosing fish slowly one at a time. Treated for every possible problem. No change. Had water professionally tested. Only issue was high chloride level. Tank has been unoccupied for six months but running. 180 gal w/ fx6. No lights at all. Turned lights on to start figuring out issue tank is full of green algae. No fish no plants no lights for 6 months. Any ideas? Don't know what to do at this point.