water - salanty

Question
Hello, I've had a 90 gal running for at least a year, most all livestock came from a 75 i had before that, lots of live rock, lots of coarls, tang snowflak eel, misc gobies and such..... here is my issue, a few corals have died off a torch and a brain..i've been adding calciam, along with balance blocks.... now suddenly my salanty has rose well past 1.30 ?? i cant figure out why ? i dod a big water change and added just some fresh water (just tonight) to get my salt level where it should be...but why did it go up so high ?

Answer
Hi Doug;

Before going any further, please remember my area is "fishing" and someone under the heading of pets might be the place to look.  Though someone more involved with tropical fish might be better able to answer your question, I have had experience with salt water aquariums that I maintained for several years as an adjunct to my fishing activities.  

The oceans of the world have become salty over the course of time because of "salts" that have gradually been dissolved from various minerals and have eventually found their way into the sea.  These salts never leave the sea and over time they only increase.  On a global basis, this takes a long, long time, measured in millions of years.  But in a much smaller habitat, this happens much more quickly.  

Salt is not just pure sodium, but any one of many chemical compounds that meet certain specifications better understood by a bio chemist.  But I am quite certain that any mineral you add to the aquarium could add to the salt content. Water, by nature is very corrosive and will dissove most natural substances and release the molecules that form salt.  The food fed to the fish may cantain a trace of salt.   The urine excreeted by the fish could contribute.  Shells, rocks, and dead corals can do the same.  These factors in an ocean are negligable, but in an aquarium, they could be significant.  

I hope this is of some help.  

-Rich