Marine aquariums can be filled with either natural seawater or synthetic water mix. Natural seawater must go through a conditioning process before being used in your aquarium. Natural seawater contains numerous microscopic organisms, both plant (phytoplankton) and animal (zooplankton). If the water is not properly conditioned by dark storage for a few weeks, the death of these organisms could radically alter the chemistry of the water, endangering your aquarium specimens.
Secondly, unconditioned water could transmit infectious diseases to your marine fish. Some aquarists prefer to collect their own water, but is is safer and more convenient to use a good quality synthetic sea salt mix.
If you do decide to collect your own seawater, it must be collected away from inshore areas that could be polluted from fertilizer runoff, sewage, heavy metals, insecticides, or other pollutants. Inshore water also contains large quantities of suspended particulates.
Collect seawater only in nontoxic plastic containers with good fitting caps. The water should be stored in closed plastic containers or glass containers for several weeks before use.
After storage, you will note on the container bottoms a fine layer of sediment that should not be added to your aquarium. After addition to the aquarium, the water should be subjected to filtration and aeration for several hours before addition of fish. It is also recommended that several water tests be conducted, including pH, ammonia, nitrite, and nitrate to insure that they are within safe levels.
