 Ca Low Alk High
HI,
I had a very bad experience that I wanted to share for anyone new to saltwater, if you starting a new tank be sure to get a good CA Kit and a good ALk kit, if you don't you will have problems. If your coraline starts to die its a warning of impending doom. your pH will go up the Alk will go up and CA will drop off and you may see white forming on everything in your tank.
You can try to dilute the problems away with frequent water changes but the Coraline algae you love to see growing maybe using up your calcium faster than the tank is using the Alk this leads low Ca that can't be easily fixed you will know cause your tank will be covered with Calcium Carbonate precip.
I have found a article that goes into great depth for a newbie about the problems that may occur.
Here's the article this web page I have printed about 1/2 of the articles and have the others on my bookmarks.
Take some time to read. A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com
This PH/ALk/Ca relation is critical to understand or you may have lots of that calcium precip and a very low calcium that can't be easily resolved with water changes.
I fixed mine by dripping slowly three quarts of that seltzer water and about 30 pH checks over two days.
And that was after a 50 % water change. yea its a battle. 
Doug
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55 GAL OP, 37 GAL SEA HORSE TANK, 5 CLARKI,
2 MARRONS,2 SERPANT STAR,1 RANDALL PISTOL,NUMEROUS HERMITS,2 SKUNKS,
4 PEPERMINT,1 ANAEMONE, SEVERAL SOFT CORALS, 2 ADULT W/C SEA HORSES,8 CHROMIS.
1 B 1 LM BLEEMY,1 WATCHMAN,1 TRUE PERCULA, 2 TANGs, 1 gold angel 1 ROYAL BEAUTY. 1 20 GAL SUMP WITH 1skimmer, 1 fluidized sand filter,
REFORGIUM, AND DSB IN MAIN AND SUMP, right handed hermits. | 
