Most beginning saltwater aquarists are concerned about creating the perfect saltwater environment for their fish and invertebrates, and rightly so. Creating the right saltwater that contains the perfect amount of salinity as well as the essential elements found in seawater is essential to the health of a saltwater aquarium.
This is not always easy, however. Sometimes it seems as though you need a PhD in chemistry just to understand all the symbols and levels and recommendations from a thousand different sources. What’s important to understand is that no saltwater aquarium is going to match the exact chemical composition of natural seawater. Whether you use natural seawater or a commercial salt mix combined with a reverse osmosis water system you can get close enough to sustain a beautiful tiny ecosystem in your home.
Some aquarists who live near an ocean actually use natural seawater as the water source for their tanks. This can be tricky, though, because even in natural seawater there can be found undesirable compounds such as pollutants and the like. If you are planning on going this route, make sure that you do not collect your water from the shoreline, as these chemicals can be found in higher concentrations here.
Another concern with seawater is that is often contains organic molecules and tiny organisms. These might not pose a problem if you are going to use the water right away, but because of that it is not appropriate to store natural seawater for any length of time.
Creating Artificial Saltwater
The natural salinity of seawater is 3.5% salt to 96.5% water. Commercial salt mixes made for reef aquariums can mimic this salinity very nicely. The problem with commercial mixes is that none of them can give you the exact chemical makeup of saltwater—seawater contains four very important ions: sodium, chloride, sulfate, and magnesium—and these ingredients often contain trace amounts of impurities when obtained commercially.
Since this is true, there is not really a way to say whether one commercial mix is superior to another. Is it more important to have too much of this chemical or too little of that. No one really has the answers. There are some chemicals that it is important to regulate, but beginning aquarists should not worry too much about whether their saltwater matches the exact composition of seawater because it won’t.
No matter what type of salt mix, make sure that your water is filtered with a reverse osmosis water system or other filtration system before use. It is also important to filter the water before topping off (which can be handled automatically with a JBJ ATO system) and with water changes. When topping off, be sure to only use filtered fresh water because the salt does not evaporate with the water.
If you are concerned about how to mix saltwater or with what salt mix to choose, ask an experienced aquarist what he or she prefers and why. You most likely will not be led wrong.