Running tank water through a kalk stirrer instead of RODI

[Epic Aquaculture]

Good evening Randy. I am currently running a kalk stirrer on my systems and instead of running the input from my RODI reservoir, I am simply running the input directly from my sump so it is being fed with tank water. Is there any problem with doing it this way such as precipitation or other chemical reactions that may cause problems?

 

[rhostam]

I did this and it worked well. Also didn’t have to worry about issues that we normally face when dosing kalk in/using RODI (such as evaporation/ salinity swings). I used a stirrer, ph probe, and schedule to ensure that the kalk reactor solution was always saturated for consistency.

I stopped using kalk because my reactor always clogged whether RODI or direct from sump and in various spots.

 

[Randy Holmes-Farley]

No, it won't work, which is precisely why it is designed to use RO/DI.

Mixing calcium hydroxide with seawater will result in precipitation of magnesium hydroxide, calcium carbonate, and magnesium carbonate, along with some trace element precipitation such as iron oxide.. Thus, one would get a lot of mud precipitate and reductions in important ions.

 

[Randy Holmes-Farley]

I did this and it worked well. Also didn’t have to worry about issues that we normally face when dosing kalk in/using RODI (such as evaporation/ salinity swings). I used a stirrer, ph probe, and schedule to ensure that the kalk reactor solution was always saturated for consistency.

I stopped using kalk because my reactor always clogged whether RODI or direct from sump and in various spots.

I think that is an incorrect assessment of what likely took place in the aquarium.

 

[rhostam]

I think that is an incorrect assessment of what likely took place in the aquarium.

Hi Randy,

You don’t think the white chalky build up clogging my dosing lines or elbows exiting the reactor was kalk?

I used an IceCap KW reactor.

Across two tanks, I positioned the unit in different spots to allow gravity feed. I used RODI exclusively. I recycled sump water. I pressurized it. I DOS’d water in and DOS’d water out. I left dosing tubes dangle above water line. I had them submerged. In every configuration, kalk clogged the line at egress of the reactor cylinder and/or at the end of the dosing tube.

Over the almost year of service (including retrofit period) when it worked, it worked well. I was lucky to get a week maybe two of use before clogging. In one case, investigating the configuration I accidentally cleared the clog and it came rushing tons of KW. I’ve had the base (where the stirrer resides) of the IceCap fill with KW so many times, it finally died (silly rust).

I’m happy to hear alternative assessments.

 

[Epic Aquaculture]

No, it won't work, which is precisely why it is designed to use RO/DI.

Mixing calcium hydroxide with seawater will result in precipitation of magnesium hydroxide, calcium carbonate, and magnesium carbonate, along with some trace element precipitation such as iron oxide.. Thus, one would get a lot of mud precipitate and reductions in important ions.

Thank you sir!

 

[Randy Holmes-Farley]

Hi Randy,

You don’t think the white chalky build up clogging my dosing lines or elbows exiting the reactor was kalk?

I used an IceCap KW reactor.

Across two tanks, I positioned the unit in different spots to allow gravity feed. I used RODI exclusively. I recycled sump water. I pressurized it. I DOS’d water in and DOS’d water out. I left dosing tubes dangle above water line. I had them submerged. In every configuration, kalk clogged the line at egress of the reactor cylinder and/or at the end of the dosing tube.

Over the almost year of service (including retrofit period) when it worked, it worked well. I was lucky to get a week maybe two of use before clogging. In one case, investigating the configuration I accidentally cleared the clog and it came rushing tons of KW. I’ve had the base (where the stirrer resides) of the IceCap fill with KW so many times, it finally died (silly rust).

I’m happy to hear alternative assessments.

When using RO/DI and a reasonably pure calcium hydroxide or oxide, the precipitate is either undissolved calcium hydroxide, or precipitated calcium carbonate as CO2 from the air enters it and becomes carbonate.

I think there's some miscommunication here.

The OP was asking about running salt water through it, and you answered it worked well for you and I suggested that shouldn't be the case.

Then you said above that you only used RO/DI.

 

[rhostam]

When using RO/DI and a reasonably pure calcium hydroxide or oxide, the precipitate is either undissolved calcium hydroxide, or precipitated calcium carbonate as CO2 from the air enters it and becomes carbonate.

I think there's some miscommunication here.

The OP was asking about running salt water through it, and you answered it worked well for you and I suggested that shouldn't be the case.

Then you said above that you only used RO/DI.

Okay. I used both sources. I was describing the gamut of stuff I while trying too counter/ troubleshooting the clogging. Apologies that wasn’t clear.

When I used sump water, I dosed sump water in, and dosed solution out from the upper 1/4 of the reactor water column. Both performed similarly in terms of Alk and ph maintenance. In fact, those two parameters were never more stable. However, I didn’t do a chemical analysis to observe the negative side effects you describe (and to be clear that I don’t doubt). I did wonder why this wasn’t done more, though, but I never came across anything that was helpful and I didn’t think to ask here.