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Cleaning a Large Koi Pond: Sludge Removal and Algae Prevention

Your Plan Is Good—With Cautions

Drain 18 inches: OK.
Clean liner algae: Gentle brushing; don't power-wash (destroys biofilm).
Vacuum sludge: Use a Pondovac or similar; work slowly to avoid hydrogen sulfide release.
Clean filter: Rinse media in pond water, not tap water.
Add "Pond Clear" (bacteria): Good.
Refill with dechlorinated water.

Long-Term Algae Control

Physical removal doesn't last. Implement: 60% plant shade, weekly bacteria, barley straw, proper feeding, and a correctly sized biofilter. See fishpondinfo.com/plants/algae2.htm.

Pond and Water Gardening: Winterizing a Koi Pond in North Carolina; Fixing a Murky Concrete Pond Without Fish; Green Water Returns in 3 Days After Full Cleanout: Filter Capacity & Biology; Fastest Way to Drain a Vandalized Pond for Cleanup; Runoff-Fed Pond Will Never Clear: Convert to Water Garden; Cesspool-Smelling Large Pond: No Outlet = Stagnation Death; Restoring a Large Natural Spring-Fed Pond; Cleaning Pond Rocks and Evaluating the Eco Aqualizer Ionizer; Natural Algae Control in a Farm Pond: Floaters and Barley Straw; Pond Additives Overload: Trust Your Established System

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