There are essentially 2 different ways to set up a Marine Aquarium – Fish Only or a Reef System, reef systems contain Coral, Live Rock, Crabs and/or Shrimp in addition to Fish. Their care requirements are different to those of freshwater fish however, and their tolerance for variations in parameters such as temperature and pH is less than that of freshwater fish. The ocean is remarkably stable, with very little fluctuation on a daily or even annual basis, and for that reason it is very important to maintain a stable environment for any Marine fish held in an aquarium. It is important to spend time in establishing the tank well before adding any fish, and to monitor the conditions in the tank regularly once it is established. Many people achieve this, with the establishment of a regular routine and a few good maintenance habits.