Filamentous Algae Identification & Treatment
Category: Algae — Filamentous Tier: 1 — High-Priority
← Back to Plant Identification Guide | Product Cross-Reference
Identification
Filamentous algae form hair-like strands that aggregate into slimy mats. Growth often starts on the pond bottom, then floats to the surface as gas bubbles become trapped. Feels slimy and stringy when handled. Often called "pond moss," "pond scum," or "blanket weed."
Types include Spirogyra (bright green, silky), Cladophora (coarse, branching, darker green), and Pithophora (cotton-like, dark green to black — "cotton ball algae").
Key distinguishing features:
- Long, hair-like strands forming mats or clumps
- Slimy, stringy texture when handled
- Often starts on the bottom, floats up with trapped gas bubbles
- Can be lifted from water in sheets
Commonly confused with: Submerged plants (have identifiable stems and leaves), planktonic algae (dissolved in water, not stringy), chara (gritty texture, garlic odor)
Treatment
Recommended Natural Waterscapes Products:
- Hydrothol Granular (endothall) — Sinks to the bottom where filamentous algae originates. Hydrothol Granular
- Copper-based algaecides (Cutrine Plus) — Applied directly to floating mats.
- Beneficial Bacteria — Reduces nutrients. Pond Cleanse Bacteria
- Pond Dye — Reduces light penetration. Vivid Blue Pond Dye
- Aeration — Increases dissolved oxygen and circulation. Aerators
Note on Pithophora: This type is particularly difficult to treat and does not decompose easily after treatment.
Full Profile
- Native Range: Ubiquitous worldwide
- US Distribution: All 50 states. Most common in shallow, clear, nutrient-rich ponds.
- Ecological Benefits: Provides invertebrate habitat and is grazed by some fish. In moderate amounts, contributes to the food web.
- Seasonal Behavior: First appears in spring in shallow areas. Peaks in summer. Pithophora can persist year-round.
Sources: Texas A&M AquaPlant – Filamentous Algae
Related
← Back to Plant Identification Guide
Natural Waterscapes — Expert Aquatic Plant Identification & Treatment