Fixing Cloudy Pond Water and Black-Coated Waterfall Rocks

Diagnosing the Problem

Cloudy water that isn't green, combined with a black coating on waterfall rocks, suggests a few possibilities: tannins from leaves/mulch, manganese/iron precipitation, or a biofilm of sulfur-reducing bacteria. The fact that it started after a liner repair and washing points to disturbed sediment or introduced organics.

Immediate Steps

1. Test water parameters: pH, KH, GH, ammonia, nitrite, nitrate, and iron. This rules out chemical imbalances.
2. Install a UV clarifier: If you don't have one, add a properly sized UV unit. It clears suspended bacteria and algae that cause cloudiness.
3. Clean the rocks carefully: Scrub the black coating off waterfall rocks with a brush *outside* the pond. If you must use a cleaner, use a pond-safe product or vinegar—never chlorine where runoff can enter the pond.
4. Add activated carbon: Place a mesh bag of carbon in the filter or waterfall to absorb tannins and organics.

Long-Term Clarity

• Establish a healthy plant population (submerged, marginal, floating) to compete for nutrients.
• Ensure your biofilter is mature and not undersized.
• Run the pump 24/7 for consistent circulation and oxygenation.
• Perform partial water changes (10–20% weekly) using dechlorinated water.

Salt is not a cure for cloudiness. Only add salt (0.1–0.2%) if you have a specific parasite or stress issue, and only if you have no salt-sensitive plants.