Will a rodi remove the hardness from my water

[Jstadler]

I've got very high ALK in my water change water, and was wondering if a RODI will take the hardness out of my water, in effect lowering my ALK. My tank water is testing in the 15 DKH and I tested my mixed change water and it tested in the 20's. Looking for opinions. Thanks in advance.

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[BeakerBob]

Originally Posted by Jstadler

...... was wondering if a RODI will take the hardness out of my water.....

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Yes, the use of RODI will remove the minerals that make water hard (ie calcium, magnesium, iron, etc.) through use of a water permeable membrane (RO) and ion exchange (DI) process. A measurement of this process is by a TDS meter that will measure the Total Dissolved Solids in the output RODI water. This TDS measurement is non-specific and will measure all solids that are dissolved in the water, not just the minerals that cause hardness like calcium or magnesium. So if the efficiency of the RODI unit is getting bad because the membranes & ion exchange media needs changing, you will see the TDS measurements increasing from the norm.

Mixing a 15 dKH alk tank water with a higher 20 dKH alk change water will increase the total tank alkalinity. This increase will depend on the amounts of each that have been mixed together. You can reduce a high alk situation a couple ways: add low alk change water from a functioning RODI unit; or, if dosing, just dose calcium supplement and not the alk for a week and remeasure.

[Jstadler]

Bob. Thanks for your response. I have some brighwell reef code A And B, I haven't been dozing with it my cal stays pretty steady at 420-440. So your saying I can just dose the A and it will intern bring my alk down? How heavy should I dose, and how high is too high for cal?


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[rmalone]

If the water your using to make saltwater is at 15dkh, your not going to see a huge drop in alk just by removing the alk portion of a 2 part. As Bob stated ro filtering will drop the alk of your base water substantially. Add in deionization and alk levels of your base water should approach zero. When you add your salt, assuming it's formulated properly, your alk will rise to acceptable levels.

[Jstadler]

Thanks for the info guys. I'm gonna stop at the LFS and buy a couple gallons of RO from them, mix it up with my salt and test that. In the meantime looks like I've got to research what system will be best for my application.