New salt less DKH than target Alk

Miami Reef · Jun 27, 2021

I’m a bit confused about this. My target alk is 8dkh and the salt mix is 7dkh.

If I fine tune my dosing pump to maintain at 8dkh. Then I do a 10% water change so does that now mean my alk is maintaining at a lower dkh?

Or does that mean corals will consume less available alk until it rises back up to 8dkh and maintains itself? Would it be better to add alk to the salt mix to bring it to 8dkh?

@Randy Holmes-Farley

RobB'z Reef · Jun 27, 2021

Dose your new salt to 8dkh before adding. If you add salt water with a lower dKH it will bring down your tank proportional to the percentage of water you change. So if you did a 50% change with 7dkh new salt your new dKH in your tank would be 7.5.

Miami Reef · Jun 27, 2021

Can I use soda ash to dose?

Jekyl · Jun 27, 2021

Miami Reef said:
Can I use soda ash to dose?

That or baking soda works just fine. Here's an easy calculator.

Reef Chemistry Calculator

Garf · Jun 27, 2021

Miami Reef said:
I’m a bit confused about this. My target alk is 8dkh and the salt mix is 7dkh.

If I fine tune my dosing pump to maintain at 8dkh. Then I do a 10% water change so does that now mean my alk is maintaining at a lower dkh?

Or does that mean corals will consume less available alk until it rises back up to 8dkh and maintains itself? Would it be better to add alk to the salt mix to bring it to 8dkh?

@Randy Holmes-Farley

Are you sure you’ve got it at the proper s.g.?

Randy Holmes-Farley · Jun 28, 2021

It's not unusual for the salt mix for water change to not exactly match the tank. You just need to account for that when doing water changes.

in this case, a salt mix at 7 dKH and a tank at 8 dKH, with a 15% change, the alk drops from 8 dKH to 7.85 dKH. It's not much of a drop.

You can accept the slightly lower alk, you can dose the tank, or you can dose the salt mix. I'd use baking soda.

Miami Reef · Jun 28, 2021

Randy Holmes-Farley said:
It's not unusual for the salt mix for water change to not exactly match the tank. You just need to account for that when doing water changes.

in this case, a salt mix at 7 dKH and a tank at 8 dKH, with a 15% change, the alk drops from 8 dKH to 7.85 dKH. It's not much of a drop.

You can accept the slightly lower alk, you can dose the tank, or you can dose the salt mix. I'd use baking soda.

Baking soda from supermarket?