Identifying and Controlling Egeria densa in a Spring-Fed Trout Pond

Manual removal: Rake/pull all visible fragments. Only sure eradication.
Grass carp: Effective but may eat desired plants; check regulations.
Benthic barrier: Bottom mats block light; impractical in 14 ft depth.
Herbicides: Diquat, fluridone—require permits, affect non-target plants.

Figure-8 pond (20x80 ft, 3–14 ft deep, spring-fed, 16 rainbow trout) has a weed that turns to dust when dry. Owner asks ID and eradication.

Likely ID: Egeria densa (Brazilian Elodea)

Submerged, spreads by runners (not spores/seeds). Once visibly removed, it’s gone—no seed bank. But manual removal must be total.

Egeria provides oxygen, habitat, and nutrient uptake. It’s not “bad” ecologically—just unsightly. In a trout pond, it may support forage.

Pond and Water Gardening: Pond Liner vs. Concrete: Which to Choose?; Clearing Green Water in a Fishless Pond; Fixing a Murky Concrete Pond Without Fish; Restoring a Neglected Backyard Pond for Safe Swimming; pH Adjustment for Fish Transfer: Raise Old Pond, Not Lower New; Overwintering Pond Goldfish: When to Bring Them Inside; Pond Volume & Pump Size Calculator; Seaming Two Pond Liners at a Waterfall: Step-by-Step for a Leak-Proof Join; High Alkalinity Well Water (pH 9) in a Montana Pond: Lowering KH Safely; Controlling Pond Weeds and Naturalizing the Edge of a Half-Acre Pond

Garden Articles

Plants