What types of fish need heaters?

Many tropical and subtropical fish need water temperatures between 75-85°F (24-29°C) to survive. These fish, including species like angelfish, discus fish, and tetras, are not able to regulate their body temperatures and rely on the external environment to stay warm. If the temperature of their tank drops below their preferred range, they can become sluggish, lose their appetite, and eventually develop health problems. In order to keep these types of fish healthy and thriving, an aquarium heater is necessary to maintain the appropriate water temperature.

Some coldwater fish, like goldfish and koi, can tolerate a wider range of temperatures and may not necessarily need a heater. However, if you live in a region with significant fluctuations in temperature, a heater can help to provide stable and comfortable conditions for your coldwater fish.

It's important to note that not all fish need or tolerate warm water. Some species, such as goldfish, koi, and loaches, prefer cooler temperatures and may be stressed or harmed if kept in water that is too warm. Researching the specific care requirements of your chosen fish species will help you determine whether or not a heater is necessary.

In addition to providing optimal temperature for the fish, aquarium heaters can also help to prevent the growth of harmful bacteria and parasites that may thrive in cooler temperatures. By maintaining proper water temperature, you can help ensure the overall health and well-being of your aquarium inhabitants.