Related Clues:

• Part of a pond problem
• Aquatic organisms
• Primitive water organism
• Chlorophyll-containing microorganism
• Lake floaters
• Bottom-of-the-food-chain organisms
• Pond organisms
• Spirogyra, e.g.
• Birdbath gunk
• Aquarium buildup
• Big oxygen producer
• Lake organism
• Bit of ocean life
• Bits of plankton
• Primitive plant