Related Clues:

• Pond refuse
• Dross
• Pond gunk
• Pond floater
• Sushi ingredient
• Tilex target
• Pond scum
• It may fill up your tank
• Seaweed, e.g.
• Pool owner's bane
• Pond greenery
• Surface residue
• Fruit of the oak
• Seaweed and kelp, e.g.
• Birdbath greenery?