In your pond, everything is temperature related. A pond thermometer is an important tool. When changing pond water, adding too much cold water at one time can cause fish stress. Doing anything different may stress out fish and cause problems. Add large volumes of water over a few days. Add Stress Coat conditioner when moving fish or adding tap water. Beneficial bacteria must be introduced to your pond and bio filter now, before feeding fish. Waste eating bacteria must be available to break down solid waste, ammonia and nitrites that are toxic to fish. They also dissolve pond plant waste and debris that blow into the pond and pollute the water. As water temperature rises above 10 C or 50 F, begin to slowly feed fish with a low temperature fish food. Fish digest this easy and waste less. As temperature rises above 18 C or 65 F, feed with summer food until late summer. Begin to run your pump now.