Kalk Rx & Alk

[Joe Grubbs]

Changed to a Kalk Rx after 10+ years of running a CaRx on a 250g Mixed Reef system (fish, SPS, LPS, Soft, etc), tank pH had run 7.8 to 7.95 with Alk running 9.5 to 10.2 kh.

Currently, with a Kalk Rx, the pH is 8.05 to 8.15 with Alk at a steady 8.3 kh dosing 2.03 g/day across 48 - 3.5 min dosing cycles using a 50 ml/min dose pump (OSC 000:00/003:30/026:00 Then ON). The Kalk Rx is a pump driven mix solution from Precision Marine (PM).

Why did I change...the 3rd recirc pump on the CaRx failed this time the magnet of the rotor split and routine ICP testing alerted me to the issue with a startling increase in Zn contaminants at 34 µg/l (8x the recommended level of 4µg/l).

So, with the Kalk Rx online, I thought the goal would be to have pH between 8.3 and 8.5 with Alk about 9.5 kh.

However, I've reached the 'stopping point' for any further dosing with the Kalk Rx...I'm limited by the amount of make up water required per day. The ATO system now cycles once every 6-8 days and my Ca levels are now climbing, > 450 ppm and rising. (A good time to buy more coral.)

For those of you who use a Kalk Rx to dose Ca and Alk:

• Since I can dose additional alk in the form of Soda Ash or Sodium BiCarbonate to obtain a higher dkh do you??

• And a second question, what is the Alk (dkh) your system has settled out at if you use just Kalk dosing??

 

[ZaneTer]

It may sound silly but you could add a small fan to increase evaporation but that also need to be offset against cooling.

 

[Joe Grubbs]

It may sound silly but you could add a small fan to increase evaporation but that also need to be offset against cooling.

Not a silly at all, I now have 2 small fans running when the tank temp rises to 78 deg f...they use to be set to turn on 79.5 with the chiller starting at 80.5 deg f. My heater turns off at 77.5 deg f. In the following temp graph, you can see where I changed the program 5 day ago...I like your idea!

 

[ZaneTer]

I’m glad you like it. It was a shot in the dark. I’m not sure how it will cope in winter (I don’t know when your dry season is)

 

[Randy Holmes-Farley]

pH is determined ONLY by the CO2 level and the alkalinity. There are a number of good ways to raise pH by lowering CO2.

Adding hydroxide (as in limewater/ kalkwasser) boosts alkalinity and depletes CO2.

Thus, the pH you end up add depends entirely on how much you can add without alkalinity getting too high, or if using limewater, on the daily evaporation r ate), and also on the CO2 in the air the tank is being aerated with.

This, there's no significance to what someone else gets for pH to what you should get.

FWIW, you can use a two part that uses hydroxide instead of bicarbonate or carbonate to add as much as you want within the limit of not boost alkalinity too high.

 

[Joe Grubbs]

Still looking to hear from those of you who use a Kalk Rx to dose Ca and Alk:

• Since I can dose additional alk in the form of Hydroxide, Soda Ash, or Sodium BiCarbonate to obtain a higher dkh do you??

• And a second question, what is the Alk (dkh) your system has settled out at if you use just Kalk dosing??

 

[Randy Holmes-Farley]

FWIW, I used just limewater/kalkwasser from a reservoir for 20 years without adding additional alkalinity, but I rarely measured the alkalinity.

 

[Joe Grubbs]

FWIW, I used just limewater/kalkwasser from a reservoir for 20 years without adding additional alkalinity, but I rarely measured the alkalinity.

Thanks.

 

[Joe Grubbs]

Still looking to hear from those of you who use a Kalk Rx to dose Ca and Alk:

• Since I can dose additional alk in the form of Hydroxide, Soda Ash, or Sodium BiCarbonate to obtain a higher dkh do you??

• And a second question, what is the Alk (dkh) your system has settled out at if you use just Kalk dosing??

 

[hart24601]

I just switched from kalk to the new 2 part with hydroxide. Honestly with the new 2 part recipe being used more I think kalk use is going to drop quite a bit.

 

[Joe Grubbs]

I just switched from kalk to the new 2 part with hydroxide. Honestly with the new 2 part recipe being used more I think kalk use is going to drop quite a bit.

Hello @hart24601, can you link me to more information on the 2 part you are using?

 

[hart24601]

Here you go!

https://www.reef2reef.com/threads/new-diy-two-part-recipes-with-higher-ph-boost.344500/

 

[Joe Grubbs]

Update:

My tank is consuming more Alk than can be provided by the Kalk Rx and managed via evaporation. Kalk dose is 1 gal/day along with 48 ml/day BRS Soda Ash... pH generally runs between 8.1 and 8.3...

I will have to decrease further the Kalk dose rate as the evaporation rate continues to decrease with the weather cooling off. My heaters are running more often than not and the fans are almost constantly on.

I find also that Ca & Mg continue to fall... requiring an additional 2 part dosing of Ca is 15 ml/day (1000 ml corrective dose) to bump back up to 420 from 345. and for Mg ... and an additional 2 part dosing increased of 20 ml/day following a 3000 ml corrective dose to get back to 1400 from 1200.

So, I'm considering re-starting the CaRx and running it alongside the Kalk Rx. Apart from the low pH, Alk was steady at 9.8, Ca steady at 400, and Mg reasonably steady at 1400... pH ran from 7.8 to 7.9...

 

[chipmunkofdoom2]

I find also that Ca & Mg continue to fall... requiring an additional 2 part dosing of Ca is 15 ml/day (1000 ml corrective dose) to bump back up to 420 from 345. and for Mg ... and an additional 2 part dosing increased of 20 ml/day following a 3000 ml corrective dose to get back to 1400 from 1200.

This is to be expected. If you're dosing the alkalinity of a two-part, you need to be dosing the magnesium and calcium portions as well. This is in part because the values are dropping, but also because dosing only sodium carbonate/bicarbonate will over time lead to an over-abundance of sodium in your system. The calcium and magnesium parts of a quality two-part contain the chloride and sulfate required to keep the major ions balanced.

 

[Randy Holmes-Farley]

So, I'm considering re-starting the CaRx and running it alongside the Kalk Rx. Apart from the low pH, Alk was steady at 9.8, Ca steady at 400, and Mg reasonably steady at 1400... pH ran from 7.8 to 7.9...

There may be good reasons to run a reactor, but dosing of a good two part should be able to stabilize the big three just as well.

 

[Joe Grubbs]

There may be good reasons to run a reactor, but dosing of a good two part should be able to stabilize the big three just as well.

It seems that I'm mixing a lot of BRS 2-Part... and surely have not made it back to balanced since turning off the CaRx...

 

[Joe Grubbs]

So, It's been over a year without the CaRx. I would summarize the past year as 'just ok'. The Kalk Rx that I started with utilized a MJ400 to stir...while the mixing was great and the saturated mix ran in the neighbor hood of 3800 ppt, the impellers did not last long...changed to a Reef Octopus with a string paddle in the bottom/motor on top...this generally created a saturated mix around 2000 ppt and has been a challenge to maintain the level the sump, fans help and the ATO runs about once a week. A recent addition to this Rx is a 50ml/min BRS dosing pump to pull from the Rx outlet and feed back to the DI inlet, timed to run when the mixer is running. This did increase the saturation to over 3000 ppt and should greatly help with the ATO challenge.

I did reach a stable time with both Kalk Rxs and will stress the importance of daily monitoring Alk. Beyond the obvious need to match the tank's need but, this is the first indication that the Kalk Rx could use another dose of Kalk, even though there was still a 1/2" of kalk in the bottom of the Rx, confirmed by the reduction in the Rx's output of 1900ppt and falling.

PH has been much better as it moves between 8.0 and 8.2.

All said, I'm still on the fence with the CaRx. I have re-built the pump and have it ready to set back up...maybe one day.

 

[Randy Holmes-Farley]

How are you measuring the levels in ppt, and ppt of what?