Related Clues:

• Eukaryotic organism
• Aquarium annoyance
• See 43-Down
• Tiny aquatic plant
• Pond dweller
• Nonflowering plant
• Sphagnum, for one
• Sargassum, e.g.
• Simple water dweller
• Marine growth
• Forest undergrowth
• It creates energy through photosynthesis
• Rock growth
• Bit of pond scum
• Chlorophyllous organism