Freshwater

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Part IV: Breeding and Other Fun Stuff
Many fish and invertebrates do not mix well. Marine fish such as the parrotfish
enjoy eating several types of invertebrates. To set up an aquarium with
marine fish and invertebrates that can live together in relative harmony without
destroying each other, you will have to do a lot of research.
Comparing Freshwater and Saltwater
Systems
There are a few pros and cons to marine and freshwater aquariums that you
should consider.
Adaptability
Freshwater aquarium fish originally came from rivers and lakes that are constantly
in motion and affected by changing temperatures and conditions.
A large majority of freshwater aquatic pets are bred for the fishkeeping industry,
but they are still naturally resistant to fluctuations in their environment
due to genetic adaptation. This does not mean you should keep freshwater
fish in less than excellent aquarium conditions, but freshwater fish will generally
be a bit more forgiving of mistakes than marine species.
Marine species are much more sensitive to even slight fluctuations in their
aquarium conditions. This does not mean that they will automatically die the
second your water temperature drops one degree. However, if the marine
species tank does not remain consistent in temperature and salinity (amount
of salt in the water), you could easily lose an entire tankful of fish.
Availability
It is generally much easier to find live plants for a freshwater aquarium than
it is to find invertebrates for a marine tank in local stores. However, marine
invertebrates can be easily purchased over the Intranet. You may have to
wait for certain species of marine invertebrates and fish to become available
as divers bring them in. Thankfully, more hobbyists and aquarium industry
folks are beginning to find ways to breed more species of marine fish.