Strange issue with high calcium

[tdyrkacz]

I have a very strange issue happening with my Calcium going up even though I am not dosing any.

My tank is only about 4 months old. 2 weeks ago when i measured calcium it was at 412. I decided to raise it to 450 and used the BRS calculator to figure out how much to dose. I did about 2/3 of what they recommended over the course of 2 days and measured again. It was at 470... i stopped dosing at this time. Fast forward a week and it's at 580... that was last night. I did a 10% water change and this morning tested again and it's at 595. I use the Hanna checker for this.

I use Tropic Marin Pro Salt. I will make another batch just so that i can test the salt.
My dkh is at 9 and i dose a little bit of alk to maintain that.
My water looks a bit cloudy today.

I have seen a few threads like this one without any real answers, but I'm hopeful you folks can help me think of something that might be contributing to this.
BTW i tested my RODI and it shows 16ppm. I ordered new resin to get that down to 1ppm.

 

[tdyrkacz]

as far as the 16ppm i am referring to TDS not calcium

 

[Randy Holmes-Farley Verified Community Expert]

The Hanna calcium checker is not known for great accuracy in hobbyists hands. I think it unlikely your calcium rose that much without dosing any.

 

[tdyrkacz]

I believe you are correct. I took a water sample to a LFS and they measured 440... I actually think i ran into this same issue 7 or so years ago when i first got into the hobby... I think the problem is I was trying to use RODI water instead of deionized water. I learned this 7 years ago and had to learn it again today.

 

[nereefpat]

I think the problem is I was trying to use RODI water instead of deionized water.

I don't know what you mean here. Those are the same thing for our purposes. RODI is Reverse Osmosis then Deionized water.

It sounds like the Hanna Ca checker is dealing you fits. You might consider getting a kit that's a simple titration, like API or Salifert.

 

[tdyrkacz]

I'm not a chemist so can't really speak to the differences between RODI and deionized, but i was under the impression they are different. I have also seen a number of threads today with people dealing with this exact issue and many of them started having better results when they used store bought deionized water instead of their RODI... in fact this was me 7 years ago. I did not have any problems with the hanna checker after that. I will try doing the same again to see if i can get results consistent with other test kits.

 

[nereefpat]

I'm not a chemist so can't really speak to the differences between RODI and deionized, but i was under the impression they are different.

You mean distilled, maybe?

Anyway, I suspect that most reefers make our own RODI water at home. If the TDS of your RODI is 16 ppm, then that does need addressed until you see a value closer to zero.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, I think he means distilled.

True deionized water would also work well, but home RO/DI (even with the DI meaning deionized) rarely is true megeohm deionized water.