What is the ideal target dissolved oxygen level for fish in a tank?

The ideal target dissolved oxygen level for fish in a tank is typically between 95-100% saturation. This range is critical because fish require adequate dissolved oxygen in their environment to thrive and maintain their metabolic functions. Dissolved oxygen levels that are around or slightly below saturation can lead to respiratory distress in fish, reduced growth rates, and increased susceptibility to disease.

Reaching levels of 95-100% oxygen saturation means that water can adequately support aerobic respiration without causing stress or harm. While dissolved oxygen can be higher than 100% under certain conditions (such as through vigorous aeration or photosynthesis by aquatic plants), prolonged exposure to such elevated levels may lead to gas bubble disease in fish, which is harmful. Therefore, maintaining oxygen levels within the 95-100% range strikes an essential balance for fish health in an aquarium setting.