Kalk Dosing and Auto Water Change

ubiq · Jan 5, 2021

Just set up an auto water change (25% weekly, constant) and I'm wondering if all the "new" saltwater obviates the need for kalk dosing. I use IO Reef Crystals which contains calcium and just have 10 frag-sized corals in the tank. I suspect that the constant infusion (3.5 gals. daily) should be more than enough to cover any calcium depletion. Thoughts?

tsouth · Jan 5, 2021

Test it.

Note params
Remove the kalk, run ATO clean
1 week duration
Test, analyze, then supplement with kalk if needed, or heck maybe even cut down the water change - you never know

The variance you receive here on the forum will not be worth its weight in gold. Your tank is 100% unique to your inhabitants and its intake in those supplements. The only true way to find the answer you're looking for is to experiment.

Best of luck to you and please do follow up with how your experiment goes!

tsouth · Jan 5, 2021

PS. Love your avatar pic

Randy Holmes-Farley · Jan 5, 2021

ubiq said:
Just set up an auto water change (25% weekly, constant) and I'm wondering if all the "new" saltwater obviates the need for kalk dosing. I use IO Reef Crystals which contains calcium and just have 10 frag-sized corals in the tank. I suspect that the constant infusion (3.5 gals. daily) should be more than enough to cover any calcium depletion. Thoughts?

Unlikely.

If the new salt water is 11 dKH and the tank is 8 dKH, 25% weekly change adds only 0.75 dKH per WEEK. Only 0.1 dKH per day.

That's almost nothing.

Randy Holmes-Farley · Jan 5, 2021

tsouth said:
The variance you receive here on the forum will not be worth its weight in gold. Your tank is 100% unique to your inhabitants and its intake in those supplements. The only true way to find the answer you're looking for is to experiment.

Is it?

Sounds like a triumph of "we cannot know anything" lol

FWIW, it is a trivial calculation to see how much it will add relative to his limewater additions.

tsouth · Jan 5, 2021

Randy Holmes-Farley said:
Is it?

Sounds like a triumph of "we cannot know anything" lol

FWIW, it is a trivial calculation to see how much it will add relative to his limewater additions.

I stand corrected. Would you please write out and share the calculation with its values? I'd like to learn it and be able to provide better, smarter answers moving forwards. Ty in advance!

tsouth · Jan 5, 2021

I think I figured it out:

(11-8) (The difference in Alk between Reef crystals and intended level) * 0.25(water change %) = 0.75 dkh/week

So you would then calculate your consumption/week, then redo the calc above to match that, which equals how much you would need to change.

Is this accurate?

So if we further calculate it and suspect you need to double it at 1.5dkh/week (your consumption rate), you can alter the water change values from 3.5g to 7g/day on a 98 gallon system.

Randy Holmes-Farley · Jan 5, 2021

Yes, that’s the calculation method I used. His real values would be needed, and then use this calculator to see how much alk his current kalkwasser is adding, and compare them:

Reef Chemistry Calculator

Adding about 1% of the tank water volume daily is about 1.2 dKH per day.