Why Are Gills Red?

No matter if a fish is sick or not, fish gills are often red – blood red, to be exact. That is because gills have blood vessels very close to their external surface.

Why is my fish's gills red?

High levels of ammonia can buildup in your fish tank. This often occurs when a tank is newly set up or when too many new fish are added at the same time. Symptoms include red or purple gills and/or fish gasping for breath at the water surface. The ammonia level can be reduced by a neutralizer and by a 50% water change.

Why gills are rich in blood?

Gills are branching organs located on the side of fish heads that have many, many small blood vessels called capillaries. As the fish opens its mouth, water runs over the gills, and blood in the capillaries picks up oxygen that's dissolved in the water.