When you have had a salt water fish aquarium for a long time, toxic ammonia from the fish's waste will naturally break down into nitrite because of the bacteria that is present in the tank. With a beginner salt water fish tank, however, the bacteria are not there yet and it can take as long as six weeks for them to multiply to the point where they are ready to break down the waste of a decent group of fish. This is why new salt water aquarium fish hobbyists should let their tanks go through a break in cycle before they actually introduce the fish to the environment. Some people may think that because they are using an older salt water fish aquarium, that they will not have to go through this break-in cycle, but this is simply not true. Whether it is a brand new beginner salt water fish tank or an old relic that you just dragged out of the attic, it will still need some time to build up helpful bacteria.
Salt water aquarium fish shouldn't be surrounded by too much bacteria to the point where they get sick, of course, but just enough of it where their waste is broken down to manageable nitrate. A beginner salt water fish tank can be broken in by adding a few hardy fish and simply waiting out that first month, but hobbyists must remember that the cycling process doesn't begin until fish are added. Some hobbyists set up their salt water fish aquarium for weeks or even months before adding fish, and are surprised to see high ammonia and nitrite readings shortly after adding the fish. Anywhere from two to five inches of salt water aquarium fish may be used per ten gallons of water. Any fewer, and the salt water fish aquarium may go through another, but lesser, cycle when more fish are added later; any more and the ammonia and nitrite levels may rise to a deadly level.
