How often should I change the water in my fish tank to ensure a healthy environment for my aquatic companions? Is there a specific schedule that I should adhere to, or does it depend on various factors such as the size of the tank, the number of fish, and the filtration system employed? Moreover, could water conditioner use play a pivotal role in determining the frequency of water changes? Should I take into account the types of fish I have, as some species may produce more waste than others, consequently necessitating more frequent changes? What implications arise from neglecting the water change schedule, particularly concerning water quality parameters like ammonia and nitrate levels? How can I discern when a water change is urgently required versus when it can be postponed? Ultimately, what best practices should be implemented for both routine changes and emergency situations to maintain an optimal habitat for my fish?