Related Clues:

• Pond-surface matter
• Floating green layer
• Mr. Clean target
• Worst of the population
• Fish tank buildup
• Growth on some ponds
• Not a nice film?
• Ugly pond film
• Surface gunk
• Film you don't want to see
• Aquarium concern
• Despicable people
• Nasty film
• Bathtub ring gunk
• Shower-door buildup