After beginning your first tank, it’s important to watch the water to verify that there are no chemical spikes that can harm your fish. Testing the water quality may help identify the reason for ailing fish or a dingy tank, but it’s still a good apply to run exams frequently even when nothing seems mistaken, about once a month. We advocate the API Freshwater Master Test Kit, which incorporates all the important thing water exams you could ever want for a freshwater tank.