Thermostat Tricks for Healthy Fish Temperature is the unsung hero in the world of fish keeping. Consider it a silent language your fish understand perfectly, waiting for you to catch on. Goldfish, for example, thrive in cooler waters, happy in the 50s and 60s. Meanwhile, tropical fish like discus or angels love it warm, basking in waters as high as 90 degrees. Finding the right temperature is essential for their health and long life. So, next time you adjust your aquarium, think of it as creatin