A saltwater tank replicates the conditions found in an ocean, while a freshwater aquarium simulates the type of water found in a lake, pond or stream. Many of the care and maintenance requirements for both types of tanks are similar, such as daily feeding, weekly water changes and regular water monitoring, but there are some major differences to take into consideration when deciding between the two.
Dollar for Dollar
Freshwater aquariums are less expensive to set up and maintain than saltwater units. Not only do saltwater fish cost much more than their freshwater counterparts, the substrate and test kits cost more. A saltwater tank also requires additional components, such as a protein skimmer, lights, salt mix and live rock. The exact cost depends on the size and setup you choose, but the initial setup cost of a saltwater tank often averages three times as much as a freshwater one.
Most freshwater fish can tolerate a wider range of water conditions than saltwater fish. This means that if you take too long between water changes or skip a cleaning, make an error or there is a sudden change in water quality, freshwater fish are more likely to survive. Beginners who are just learning to manage an aquarium may have more success with freshwater aquariums due to this increased tolerance.
Freshwater tanks can handle a larger population per gallon than saltwater aquariums. The general rule of thumb for a freshwater tank is that you can have 1 inch of fish per gallon of water, while for saltwater tanks it is 1 inch of fish per 2.5 gallons. This means you can put more fish in a freshwater tank without overcrowding.
Light It Up
Lights in freshwater aquariums are used for decorative purposes, but they're a requirement in saltwater tanks. Live rocks and plants require a certain amount of light each day in order to thrive.
Freshwater fish are usually easier to find, and in a wider range of specimens than saltwater fish. On the other hand, saltwater fish usually come in brighter colors and patterns, as well as a variety of interesting shapes, than freshwater fish, although there are many brightly colored freshwater fish species. Some species of freshwater fish are easy to breed, even for a beginner, while saltwater fish typically present much more of a challenge.