What is the solution for black Gill damage?

Brownish to blackish discoloration on the gills it's called brown/black gill diseases.

Reasons

1. High content of dissolved organic matter and turbidity
2. Poor water quality & bottom.
3. Unhealthy algae crashing & foaming.
4. Unhealthy shrimp ( secondary infection)
5. Fouling organisms, fungus, ciliated protozoan, bacteria.

Control Techniques:

1. Water exchange
2. dissolved organic matter sedimentation in the water(lime application)
3. Biotic & abiotic agent treatment (Chemical)
4. Bottom & water waste bio-degradation.
5. Avoid over feeding.
6. Sufficient aeration inputs.
7. Maintain good healthy algae in pond