Water hardness

[Tryingmybest]

Hi, I posted in here before and got great help so hoping for that again. I’ve been in the hobby for awhile but have a newer 20 gallon saltwater tank right now that was converted from a 55 gallon tank. When I had the 55 gallon everything was great and everything inside was doing amazing. Recently in my 20 gallon tank my condy anenome has been looking pretty bad and I’m pretty sure it’s going to die very soon. I think it is because of The water hardness in my tank. When I first set it up it seemed a little high when I tested it but recently its been reading pretty high. I use the imagination Pacific Ocean water because I don’t have a good fish store close to me that sells water. To top it off I use tap water that I put primer in.
Does anyone have any recommendations to help reduce the water hardness in my saltwater tank?

 

[Randy Holmes-Farley Verified Community Expert]

What do you actually mean by hardness?

GH, general hardness is not a useful measurement in seawater as it it a combination of several things, including calcium, magnesium, and strontium:

GH (general hardness)

Hardness is a characteristic of water due to the presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters (calcium and magnesium carbonates, typically), and forms insoluble solids when it reacts with soaps. Hardness is often expressed in grains per gallon, parts per million or milligrams per liter, all as calcium carbonate equivalents. It is a measure often used in freshwater aquarium systems, but not often in marine systems, where its values are very large. Seawater has a total (general) hardness of about 6.3 g/L (6,300 ppm) of calcium carbonate equivalents. These linked articles detail aspects of magnesium and calcium in seawater.