Spring is a critical time of the year for pond fish. As they come out of dormancy, their bodies are low on important nutrients that help ward off disease. Therefore, they are more likely to become vulnerable to illness. To keep the incidence of sickness to a minimum, it is important to clean out sludge and debris from the bottom of your pond as well as replace about 25% of the pond water with fresh water and treat the water with a water conditioner.
Treat tap water with a water conditioner anytime it is added to the pond to remove chlorine and chloramines and to protect the fish with a slime coating. Healthy water means a healthy ecosystem especially if you stock pond fish.
As fish make the transition from winter to spring, be sure to note visible changes in their behavior. There are distinct differences in what a healthy fish looks like as opposed to what signs a struggling fish exhibits. Fish that are sick will be gasping for air, have changes in color or an emaciated appearance, or show visible sores and spots. In spring, to make the transition from dormancy to an active state, pond fish should be fed temporarily a wheat-germ based diet only after pond water temperatures rise above 39°F. When the water temperatures reach 59°F, the fish can be fed other diets.