As Malaysia strengthens its food security agenda by expanding inland aquaculture, the health of the Selangor River basin, especially the Rawang Sub-basin, becomes more important than ever. This book reveals how fish-farming effluents influence water quality, habitat conditions, and macrobenthos communities that quietly signal the river’s ecological state. By introducing a scientifically grounded, macrobenthos-based organic pollution index, this approach offers a practical tool for balancing aquaculture growth with responsible environmental stewardship. Written in an accessible and engaging manner, the book highlights how Malaysia can pursue high-value aquaculture without compromising the integrity of its freshwater ecosystems, ensuring that economic progress and river conservation advance together.