hey guys i have a weekly pool that i do for a customer and every week for the past 3 weeks the algee is growing on the walls and the water has greenish tint. the water test is perfect every week its a salt water pool salt is around 3400 ppm . i have several pools that i service one a week and this is the only one with a problem i am starting to think it may be the actual filter since its the only pool with a cartridge filter all others are de. i have the filter set to run for about 16 hours a day. any sugestions