Freshwater

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Part IV: Breeding and Other Fun Stuff
There are not as many choices in brackish fish as there are for other systems,
because few species in the wild can survive in an environment that is constantly
changing. The good news is that brackish fish are very hardy, easy
to feed, and many are very exciting to watch due to their high activity
levels. Several plants work well in the brackish tank, including hornwort
(Ceratophyllum demersum), Vallisneria gigantea, and Vallisneria asiatica.
Saltwater Marine Aquariums
Marine or saltwater systems, not surprisingly, require saltwater. You see
marine fish on scuba and underwater television programs. The most popular
of these fish includes the coral reef species often found living in close proximity
to various invertebrates (animals without backbones). Saltwater fish are
often very colorful and beautiful. They can also be very expensive.
The saltwater in a marine system is obtained by mixing fresh water with a
manufactured salt mix available at fish shops. A good filtration system is
important in marine tanks to keep oxygen levels high and ammonia levels
low. Marine fish have lower tolerance to ammonia than freshwater species
do, and an inadequate filter soon leads to disaster in a saltwater tank.
Types of marine systems
There are three main types of saltwater aquariums:
Coldwater marine: Many tanks of this type house animals such as lobsters
and rockfish that are native to colder ocean areas.
Tropical marine: These heated tanks generally contain fish native to
coral reef areas, such as tangs, clownfish, and damsels.
Reef tank: Some reef tanks contain only invertebrates, such as
anemones and scallops and organisms growing on live rock. Live rock is
rock that has live beneficial organisms attached to it that provide food
sources for your fish and help keep the water clean.
You can set up a saltwater system in a variety of ways (see Figure 23-1 for one
example). Invertebrates are a little more difficult to care for, so if you do set
up a saltwater system you may want to start with a fish-only tank.