What typically indicates poor water quality in a fish tank?

Unusual water clarity and color is a strong indicator of poor water quality in a fish tank. Water that appears cloudy or tinted may suggest the presence of excessive suspended particles, bacterial growth, or organic matter decomposition, all of which can be harmful to fish and other aquatic life. Additionally, changes in color, such as a greenish tint due to algae or a brownish appearance from organic debris, can signal imbalances in water chemistry or excessive nutrient levels, which can negatively affect fish health.

While high fish activity levels can sometimes indicate a comfortable environment, it can also mean that fish are stressed due to poor water conditions. Algae blooms do suggest an excess of nutrients, but they also represent one aspect of broader water quality issues rather than being the sole indicator. An increase in tank temperature may also affect fish behavior and health, but it does not directly reflect water quality. Thus, unusual clarity and color in water serve as more definitive signs of underlying problems in water quality.