What is the Ideal Temperature for Aquarium Fish?

Aquarium fish come from around the globe, so different species have different water temperature preferences, and they get stressed when kept outside of their preferred temperature range. However, the vast majority of aquarium fish fit into a few categories of temperature preferences.

  1. Tropical Freshwater Fish

    • Cichlids live in the tropical regions of Africa, South America and Asia.

      Almost all common freshwater aquarium fish prefer tropical temperatures. In general, freshwater aquarium fish thrive between 76 and 82 degrees Fahrenheit. Some species -- like mollies -- prefer water at the higher end of that spectrum, and possibly even slightly warmer. Others -- like certain loaches -- need water from the colder end of the range. Always research the specific species you want to keep, since fish vary somewhat in their temperature preferences.

    Tropical Saltwater

    • Ocean fish come from very stable water and react poorly to changes in water parameters.

      Tropical marine fish have similar temperature preference to their freshwater brethren. However, ocean environments -- especially reefs -- typically resist temperature change due to the great volume of water. This means that tropical saltwater fish need temperatures between 74 and 78 degrees Fahrenheit. Certain deepwater reef species need slightly colder water, between 72 and 76 degrees. However, marine aquariums often have powerful lighting to keep coral comfortable, and these lights can sometimes overheat the water. Cooling fans and aquarium chillers may be required to keep their tanks from getting too hot.

    Goldfish and Other Freshwater Temperates

    • Goldfish need at least 30 gallons of aquarium volume per fish ideally.

      For freshwater fish, goldfish are a special case. Goldfish come from temperate and subtropical regions. As a result, they prefer water between 68 and 72 degrees Fahrenheit. Goldfish can survive higher temperatures, but it will stress them and leave them more vulnerable to diseases. Additionally, warm water doesn't hold oxygen as well as cold water, so tropical water has less oxygen than goldfish are used to. For these reasons, goldfish and tropical fish should not share an aquarium. In most cases, goldfish aquariums don't need heaters since their preferred temperatures are about comfortable room temperature.

    Temperate Marine

    • Most of the coastal regions of the U.S. are at temperate climates.

      Coldwater marine aquariums have begun to grow in popularity in recent years. Saltwater marine organism usually prefer water between 50 and 70 degrees Fahrenheit. Some temperate marine organisms can survive in temperatures up to 72 degrees, but these organisms really thrive at lower temperatures. In most cases, you will need a chiller to maintain these temperatures, since they are slightly below room temperature.