Maintaining a saltwater tank is somewhat more difficult than keeping freshwater fish. Water must be tested daily. Marine specimens as a whole are more fragile than freshwater, and any illness rapidly spreads through the tank.
The most popular decoration for a saltwater tank is live coral. The name is a misnomer, since "live coral" is actually a piece of dead coral broken off a coral reef in which algae live in the nooks and crannies. The algae help keep the water well oxygenated.
While the price of freshwater tropical fish has increased over the years, saltwater fish have always been more expensive. In addition, because of the greater sensitivity of marine specimens to fluctuations in water conditions, saltwater fish are easier to maintain in larger tanks - the bigger, the better.
There are two basic options for marine aquariums. The simpler is to have a mainly barren tank with a sandy bottom and a few decorations, such as coral rock or driftwood. The other option is to install live coral and build a coral reef within the tank.