film on acrylic tank surface

Question
The problem still exists after I have left the lights off as well as did a complete water change, and rinsed the filter medium. The slimy film on the water surface has come back.
Help.

Answer
When did you change the filter media last?  please refresh my memory is this a freshwater or saltwater tank?  What size is the tank? what kind of food are you feeding the fish? have you checked your water chemistry? if so what are the values? What is the tank temperature?  what kind of fish do you have in the tank? etc... dave