Related Clues:

• Pond scum
• It may fill up your tank
• Seaweed, e.g.
• Pool owner's bane
• Organic fertilizer
• Pond greenery
• Flammable moss
• Bog material
• Moss type
• Fuel
• ___ moss (mulch material)
• Decayed vegetable matter
• Seaweed and kelp, e.g.
• Birdbath greenery?
• -- moss