The saltwater aquarium hobby includes several different specialties, each with its own specialized care requirements. These different types of aquarium setups can house radically different types of organisms. Each kind of tank has its own distinct appeal and challenges. In fact, some even consider the challenge of keeping certain saltwater setups to be part of the fun.
The tropical fish-only setup is the starting point of the marine aquarium hobby. Marine fish, particularly tropical fish, have easier care requirements than marine invertebrates. Most of the equipment for a fish-only setup is familiar to freshwater hobbyists, with few additions, like protein skimmers. Some advocate the use of live rock -- old coral skeletons that have been colonized by other organism -- for fish-only tanks. This setup is called a Fish Only With Live Rock, or FOWLR, setup. The FOWLR setup is recommended because live rock often contains bacteria that eat fish waste, providing biological filtration. These tanks are considered the easiest saltwater aquariums, but still provide a greater challenge than most freshwater tanks.
Reef tanks require more complicated care than fish-only or FOWLR setups. In a reef tank, the reef hobbyist also maintains coral, anemones and other invertebrates that require complex care. These invertebrates demand powerful lighting, specialized equipment and pristine water conditions. Unlike the fish-only tank, live rock and protein skimmers are not optional. You also must select your fish and invertebrates with care to prevent expensive specimens from eating each other. Additionally, reef tanks require you to monitor water parameters that you never have to think about in a fish-only setup, like calcium. This is because reef tanks require supplemental calcium, since coral and other invertibrates absorb calcium from their water.
Temperate Marine Tank
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The temperate, or coldwater marine tank once was less common, but is growing in popularity. These tanks feature organisms that thrive in water between 50 and 70 degrees Fahrenheit, but ideally should remain between 60 and 65 degrees. To keep their water in this range, temperate tanks require a piece of equipment called a chiller. Chillers can be expensive, since many units contain titanium as a heat exchanger. Like a reef tank, these tanks require strong water movement. However, temperate tanks require less powerful lighting, even when they contain photosynthetic organisms, like seaweeds or cold water coral.
Believe it or not, the smaller an aquarium is, the more difficult it is to maintain. With this in mind, nano aquariums, defined as a saltwater aquarium smaller than 30 gallons, is considered one of the most challenging saltwater setups. These tanks have no margin for error, as any problem will manifest much more quickly in a smaller water volume. Despite their small size, you will want to use equipment rated for a much large aquarium to keep waste from building up. For example, a protein skimmer rated for a 100 gallon aquarium would be appropriate for a tiny five-gallon nano tank. These small aquariums also may require cooling fans to keep from overheating.