Using kalkwasser ATO with dropping alkalinity but rising pH

[Gator_Reefer]

Hi - Desperately looking for any help from folks with more experience than me......

Issue: Using 1.5 tsp per gallon of kalkwasser powder with distilled water in an ATO and still losing about 0.5 dKh daily, while Calcium seems fairly stable at 420-450 ppm, however pH is sky high at 8.6.

Tank is a mixed reef 30.2 gallon AIO with about 13 or so frags of SPS/LPS and a rock flower anem. I'm reluctant to think the alkalinity consumption from my corals is higher than what my kalkwasser ATO is supplying @ 1.5 tsp/gal concentration and thus resulting in the persistent drop in kH. However, I'm not seeing any obvious signs of abiotic preciptation (water cloudiness or significant precipitate on equipment). Also, the high pH makes me think I need to back off the kalkwasser concentration. Not sure what's going on....or if I need to abandon kalkwasser ATO (really don't want to because I like the simple setup and worked great initially) and just get dosing pumps for 2-part.

Any ideas? .....TIA.

 

[Daddy-o]

If it is stable, do worry about it. If you have issues, you could add vinegar to you mix.
Cheers! Mark

 

[nereefpat]

As long as the tank is well aerated, the pH doesn't make me panic.

What's the actual alkalinity value of the tank? Do you have a ton of coraline algae growth?

 

[Gator_Reefer]

As long as the tank is well aerated, the pH doesn't make me panic.

What's the actual alkalinity value of the tank? Do you have a ton of coraline algae growth?

Alk tonight is 6.33 dKh. I am dosing 6mls (for 30 gal tank) to keep it somewhat stable on top of the kalkwasser ATO.

So you don’t think 8.6 pH is concerning?

 

[nereefpat]

As long as the tank has aeration (powerhead at the surface, skimmer, overflow, etc) the pH *shouldn't* get too high. Sometimes our pH measurements can be off too. How do you measure it, and when did you last calibrate your probe, for example?

I would try to raise that dKH to where you want your setpoint to be with baking soda. Then adjust dosers/kalk to keep up with demand.

Anyone else have some thoughts here?

 

[YankeeTankee]

How are you testing for alk? I'd verify with another method. At a ph of 8.6 I'd back off the kalk a little.

FYI it is normal to see larger swings in alk vs calcium.

So in summary I would verify with another test kit then just dose more 2 part and back off kalk.

 

[Gator_Reefer]

Thanks for the feedback.

I am using an Apex pH probe and a handheld Hanna probe to monitor pH. Last calibration was two days ago in 7.0 and 10.0 solution.

I am using the Hanna Alk Checker. I also wondered last night if it could be my alk readings are off so I ordered some alk calibration/reference solution for the Hanna checker...we’ll see.

I switched to pure RODI for the ATO last night and skipped 2-part dosing to get a sense for actual alk consumption in the tank. I just re-tested, it consumed approx 1.0 dKH over 24 hrs. I would’ve thought 1.5 tsp of kalk per gallon in an ATO would’ve easily kept up with that demand. I’m wondering if I over-mixed the solution or if its precipitating somewhere that’s not obvious to me.

Anyway, I cleaned out the ATO pump and reservoir real good and will start the kalk mix at 1 tsp/gal to see what happens.

What still puzzles me is if it was just alk precipitation or over-mixing of the kalk solution that caused my alk readings to drop....wouldn’t the pH have dropped along with it, or at least not have risen?

 

[Randy Holmes-Farley]

The high pH greatly increases the daily demand for alk and calcium.

 

[Backreefing]

Kalk raises ph because of the hydroxide combines with co2 to make carbonate or bicorbonate . It’s a good thing about kalk .
you could raise your DKH with a variety of buffers to chose from.

 

[Gator_Reefer]

The high pH greatly increases the daily demand for alk and calcium.

Interesting Randy, so is the associated higher demand due to actual higher coral calcification (consumption) than in lower pH? If so, I guess may not be bad thing to benefit from faster growth if I can manage to keep alk stable.