Carbonate hardness

[Nanobros]

My carbonate hardness is super high. It's 20. I'm not sure how to lower it. I did a water change yesterday. I use RO Water. I tested it and it's carbonate hardness is 0. I'm using premixed saltwater from my lfs its in 5 gallons. It's carbonate hardness is 12. I'm not sure how to lower it. Please help!

 

[heathlindner25]

If you are adding pH buffer stop, either lots of water changes or time will bring it down.
Also double check for a bad test kit

 

[Nanobros]

If you are adding pH buffer stop, either lots of water changes or time will bring it down.
Also double check for a bad test kit

How do you check for a bad test kit?

 

[heathlindner25]

Get another kit and cross check.