Removing general hardness from RO tank

[NoobandknowIT]

Hello,

Is it true the only way, in a salt water system that was filled with pure RO (no DI) water mixed appropriately with good salt (using Fritz RPM salt mix, 1.025 sg), to lower CA and / or MG hardness is to do a massive water change?

TIA!

 

[laverda]

Your RO membrane should remove 98% or more of the general hardness from your tap water. No your statement is not true. Both should decline with time if you have coralline algae, some algae’s, corals that form calcium based skeletons or clams in your tank. Lower salinity will also lower them.
What are the peramaters of your newly mixed salt? If you new water has higher Ca and Mag then 100% water change will be high too! If your salinity is higher than 1.025 you will have higher ALK, Ca and Mag levels.

 

[lavoisier]

If your CA and/or Mg is high, doing a large water change (you may need to repeat a couple of times) with RODI water will lower your levels.

 

[NoobandknowIT]

So I am understanding 100%, there is no way to lower CA and / or MG in your tank other than to do a massive water change....correct? TIA