Related Clues:

• Pond problem
• Soap ___ (shower buildup)
• Bathtub residue
• Dirty film
• Birdbath gunk
• Fail to utilize
• Unnecessary cost
• Aquarium buildup
• Lowlifes
• Watermelon rind, e.g.
• Fail to use
• Slimy film
• Surface impurities
• Pond-surface film
• Slimy coating