Kalk stirrer optimization

[drsalomon]

Hi,
I reactivated my kalk stirrer since I started a calcium reactor. I am experiencing the same thing as previously with slow decrease in potency of the kalk over time. I don't want to be tied to weekly top offs of kalk powder to make the setup vacation compatible. I assume CO2 from the ATO water and CO2 entering the outlet of the stirrer are converting some of the kalk in the reactor to calcium carbonate. My fish room is held at 500 ppm max CO2 by a energy recovery ventilator (ERV). So I was thinking of having the outlet of the kalk stirrer placed under the water instead of dripping into the sump and also possibly sparging the ATO RODI water with air pumped from the room through a CO2 scrubber. Do you guys know any other tricks? I already use the Apex to control addition when the sump float sensor and pH is low to optimize pH raising effect when it is really needed.

 

[DylanCameron]

Some quick questions: how do you know you’re losing potency, do you monitor the pH of the saturated solution? How much solution are u dosing over 24 hours? Which reactor are you using? If it’s a continuous stirrer (like the avast or similar), is there anything stopping you from simply adding a larger volume of kalk powder?

Slightly unrelated but IIRC you mentioned having alkalinity swings, do you think it’s because you’re only adding kalk at night?

 

[drsalomon]

Monitoring pH or conductance of the saturated solution would be the best method. I will try that. There is no probe port on my stirrer so I would have to spot check it. I also don't have a good read on the exact volume dosed as it is a throttled down pmup in the RODI reservoir not a DOS pump. I have it set to turn on at night if the pH slips below 7.1 and runs 8pm-8am with 30 sec doses every 10 mins as the pH calls for it. It is a continuous stirrer aqua medic kalk stirrer 1000 reactor similar to the avast with a motor on top and a paddle on the bottom. I can play around with it more to see if I can get a more direct read on potency reduction. The low alk point is right around 10pm and the kalk helps me get back up during the night. The swings were coming from using ARM media in the calcium reactor and I switched to reborn today and it seems to have eliminated the swing with its higher melt rate. I just determined that sparging the RODI container with air from a CO2 scrubbed air pump had the opposite effect that I wanted. It lowered the pH which indicates net increase in CO2 in the RODI water.

 

[reefkeeper2]

Having the reactor continuously stir exposes the kalk to atmospheric CO2 more than if you stir it once and let it sit. Try putting the stirrer on a timer. I ditched my kalk stirrer for a bucket that I fill once every 3 days with fresh kalk and DI water. More labor but better results.

 

[drsalomon]

I can try that. Might you have a suggestion for the minimal amount of stirring? How about 1 min every hour?

 

[reefkeeper2]

More like one minute four times a day. It would depend on the volume of water entering the reactor. You will have to play around with it to see what is optimal.

 

[drsalomon]

Thanks for that info. If it is not stirred enough, what might I expect to see? Will it gum up?

 

[DylanCameron]

Actually this is going to depend on how fast it’s stirring. Reactors like the icecap create a vortex that breaks surface tension, but slow stirrers like the avast and some other spin it gently enough that it doesn’t break surface tension. When I had my reactor going on my 80g (avast) it was continuously stirring, and there was a layer of solid calcium carbonate (kalk crust) that actually prevents the solution from reacting with air. When your reactor is stirring, you should check to see if you have a solid layer of crust or if your surface tension is broken.

7.1 seems extremely low for pH, is that probe calibrated? This is especially odd considering you’re controlling the CO2 levels of the fish room. Again, what makes you believe the kalk is losing potency?

 

[reefkeeper2]

Thanks for that info. If it is not stirred enough, what might I expect to see? Will it gum up?

It shouldn't gum up. What Dylan said above is correct also.

 

[drsalomon]

Sorry for the typo. The switch happens at 8.1 not 7.1.