Marine aquariums normally can be defined under 3 different groups, each with their own requirements, care of livestock, and various livestock selections. Although many of the livestock can be placed into other groups, which can prove to be fatal if not properly placed into the correct environment.
- Marine aquariums are those that keep both marine plants and livestock inside. A marine aquarium mostly showcases off fish as the primary focus and to provide coloration to the tank, although some use live rock as a natural background and hiding element for some species. Live rock provides not only a natural appearance, but also acts as a natural biological filtration system as it metabolizes bacteria.
- Reef aquariums or tanks are commonly known for being a marine aquarium but instead display off more corals and other marine invertebrates rather than displaying fish as the primary focus. A reef aquarium requires more intense lighting, turbulent water movement for the corals to feed properly, and more stable water parameters than a marine aquarium.
- Brackish water is a mixture of both freshwater and marine, as the salt concentration is lower than marine levels but higher than freshwater levels. A subsection of freshwater fish can be known placed within brackish water as their natural environment varies from freshwater to some saltwater.
Marine livestock is different than it's freshwater counterpart as there as vast difference in both the adaption of the animals, the coloration that comes with marine life, and also the required care for species. Inhabitants of a marine aquarium are often costly as their care level is more difficult, but their appearance result in a unique aquarium that will stand out regardless of where it is placed.