Calculating kalkwasser dosage

Cory · Jan 29, 2016

So i did some daily measurements of my alkalinity via Hanna alk checker for about a week. Here are the resultd:

Jan 17th tests at 3am
Alk 7.44dkh
Raised to 8dkh
Po4.07

Jan 18th tests at 4am
7.72dkh
Raised to 8dkh (1gram)
Po4 .03

Jan 19th at 1am
8dkh, not corrected because of no change.
Po4 not measured

Jan 20th
7.79dkh raised to 8.1dkh (.72g)

Jan 21sr
8dkh
Po4.13ppm (scraped ats clean)

Jan 23 6am
7.72dkh
Raises to 8.1 dkh

Jan 26th
7.56dkh raised to 8dkh
Po4 .04ppm

So can someone help me calculate an amount to maintain calcium and alk with limewater? The tank has 28net gallons and evaporates between 1-2 liters per day. (Low evaporation due to glass lid on tank, sump is uncovered.)

Randy Holmes-Farley · Jan 29, 2016

You must be quite the night owl, testing at 1 AM, 3AM, 4 AM, etc.

It looks like you are using roughly 0.2 dKH per day or a bit less.

So if you add about 190 mL of saturated limewater each day, you'd be close and can adjust from there.

You could dose that all at once if you want. The pH will jump about 0.1 pH unit once dispersed through the whole tank. But slower would be better to avoid local precipitation events before it mixes in.

If you want to add that to all of your top off, add about a tenth of a teaspoon of calcium hydroxide to your daily top off.

JimWelsh · Jan 29, 2016

Between 1/17 and 1/26 your tank consumed an average of 0.155 dKh per day. Reef Chemistry Calculator says for 28 gallons, you will need 0.13 liters per day of saturated limewater.

JimWelsh · Jan 29, 2016

Between 1/17 and 1/26 your tank consumed an average of 0.155 dKh per day. Reef Chemistry Calculator says for 28 gallons, you will need 0.13 liters per day of saturated limewater.

Cory · Jan 29, 2016

Randy Holmes-Farley said:
You must be quite the night owl, testing at 1 AM, 3AM, 4 AM, etc.

It looks like you are using roughly 0.2 dKH per day or a bit less.

So if you add about 190 mL of saturated limewater each day, you'd be close and can adjust from there.

You could dose that all at once if you want. The pH will jump about 0.1 pH unit once dispersed through the whole tank. But slower would be better to avoid local precipitation events before it mixes in.

If you want to add that to all of your top off, add about a tenth of a teaspoon of calcium hydroxide to your daily top off.

Lol yeah night shift at work. We switch back and forth 6 on 3 days off 6pm-6am then after days off 6am start to 6pm finish... Like a zombie. Ehh life of an oilfield worker...

I wonder if i could add it to a compartment that the overflow drains into? The gallons in there is about 1.5 gallons. The flow is about 400gph. Or would it be better to drip it slowly?

Cory · Jan 29, 2016

JimWelsh said:
Between 1/17 and 1/26 your tank consumed an average of 0.155 dKh per day. Reef Chemistry Calculator says for 28 gallons, you will need 0.13 liters per day of saturated limewater.

To saturate it just add 2tsp per gallon right? Id check the ph for potency but its in the mail still lol

JimWelsh · Jan 29, 2016

By definition, to saturate it, add it until it won't dissolve any more! Let it settle, and take the supernatant (clear liquid on top).

Cory · Jan 29, 2016

Awesome ill try that

Cory · Feb 11, 2016

So after all this time, ive added 191ml of saturated limewater daily. Dkh is at 9. 161ppm via hanna.

How much should i reduce it?

Randy Holmes-Farley · Feb 11, 2016

That's impossible to say except by trial and error.

What do you want the alkalinity to be?

Cory · Feb 11, 2016

I think to maintain 9dkh is right in the middle of 7-11dkh. So 9 dkh is good.

Randy Holmes-Farley · Feb 12, 2016

Ah, I understand. You have reached your goal and are now concerned it may rise more?

It may not rise more, or it might continue up a bit. Do you know if it has risen noticeably in the past few days?

The higher the alk the higher the demand, so it has a negative feedback loop limiting the rise.

Cory · Feb 13, 2016

Yeah thats my concern that it may rise more.

Im not sure if its risen more in the last few days, i just tested once. It was at 8dkh when i started dosing it.

So should i try for another few days and test again at the same dose?