Most aquarium cool-water fish benefit from a winter cool down. Without it, they may not breed in the summer and colors will be dull.
Fish, like other animals and plants, use their stored fat to rejuvenate their bodies and produce eggs.
It’s best to cool down your cool-water fish gradually as sudden changes cannot be tolerated. Placing the tank in a cool room will help complete the change in 2-4 weeks. Water temperature should be no lower than 60 degrees fahrenheit. During this period, food should be kept at a minimum and there should be shorter periods of light.
After a few weeks of winter, it’s time to start gradually increasing the water temperature and light. Maintain an increase of no more than 1-2 degrees Fahrenheit daily. Food can be increased too.
Hopefully, your fish will show their approval by laying eggs and showing their brightest colors.