Calcium rising while Alk Steady?

[Caravanshaka]

I am still trying to dial in my ATI essentials dosing, so am testing calcium and Alkalinity regularly. I’ve gotten some weird results that I wanted to run by everyone before I lose my mind.

190g total volume SPS dominant tank with mostly drags at the moment.

For a few weeks now, Alk has been holding steady between 7.25-7.6. It’s going up and down a bit while I fine tune.

I realized a week into dosing that my calcium essentials DOS pump hadn’t been running even though it showed on fusion to have been dosing, so I went a week without calcium dosing. I kicked it on, and put in about 2 days worth of calcium in one day, and tested it out at 440.

This was 5 days ago, and at that point I put calcium back to the same dosage as Alk per ATI instructions.

Last night I tested Alk to have dropped about 0.1 over those 5 days, but Calcium raised to 502!!!

I immediately turned off essentials 2 and 3 to stop dosing calcium to let it drop. 24 hours later, I detest. All dropped about 0.1 in those 24 hrs (and I raised that dose for tomorrow), but calcium read 528!! I thought that couldn’t be right, so I ran the same test again and it was 587.

Both are being tested using Hanna checkers. The calcium tests were the last 3 I could get in that reagent bottle (expires in 2020). Could it have been something to do with the reagents?? I did happen to take samples for ICP testing last night, so will know for sure in a couple weeks.

What do you guys think? Chalk it up to reagent issue and continue dosing until I can get more reagents in? Stop dosing for now?

Thanks!

 

[Randy Holmes-Farley]

Lots of people have issues with the Hanna Calcium checker and I expect that may be the issue. Calcium does not rise if you are not adding it.

Hanna designed a method that is freakishly sensitive to very low levels of calcium in the blank, so the water used must be super pure.

I'd personally base the calcium dosing part on the alkalinity demand for now till you confirm the calcium reading somehow. That said, if you want to stop dosing calcium, that's fine too. Calcium moves up and down from over or under dosing much more slowly than alkalinity does, and calcium is fine in a big range from 400 to 550 ppm.

 

[Caravanshaka]

Thanks, Randy. I'm going to continue dosing calcium and see if I can get the water tested at my LFS today.

What is odd is that the last time I sent in my ICP testing, my Hanna checker was within 10 ppm on calcium when compared to their results. It just seems like the very end of the bottle of reagents has given me odd results.

 

[Caravanshaka]

Had my LFS test my water today and they got 380, which sounds a whole lot more reasonable considering the situation. Time to double up the calcium dosing again and get some new hanna reagents.

 

[Randy Holmes-Farley]

Sounds good.

Happy Reefing.

 

[Caravanshaka]

Well, got more reagents tonight and tested twice...got 468 followed by 480.

Guess I need to order a titration kit to give me a second opinion.

 

[Randy Holmes-Farley]

Well, got more reagents tonight and tested twice...got 468 followed by 480.

Guess I need to order a titration kit to give me a second opinion.

Those levels are fine, however, so don't agonize over it.

 

[Caravanshaka]

Those levels are fine, however, so don't agonize over it.

I appreciate the help, Randy!

 

[wangspeed]

It’s most likely your testing method or water you’re using. I found that the only way I could get accurate results with the Hanna Ca tester was to get a new more accurate .5ml syringe with a smaller tip, buy Hanna RODI, and never ever rinse the vial with tap water. Only rinse with my own RODI. I could get accurate repeatable results, but it’s time consuming.

I took a break from reefing after we moved, but I’m back again and I recently broke out my Hanna Ca kit. After I found that it was broken, all batteries report bad, I was actually kind of relieved. I’m going back to a Salifert for Ca.

 

[Caravanshaka]

It’s most likely your testing method or water you’re using. I found that the only way I could get accurate results with the Hanna Ca tester was to get a new more accurate .5ml syringe with a smaller tip, buy Hanna RODI, and never ever rinse the vial with tap water. Only rinse with my own RODI. I could get accurate repeatable results, but it’s time consuming.

I took a break from reefing after we moved, but I’m back again and I recently broke out my Hanna Ca kit. After I found that it was broken, all batteries report bad, I was actually kind of relieved. I’m going back to a Salifert for Ca.

Up until a couple weeks ago, I was getting accurate repeatable results that were within 10 ppm of ICP testing. I always use 0 TDS RODI for the testing and cleaning of the vials. I may try a more accurate syringe....that might help. Thanks!

 

[Randy Holmes-Farley]

Up until a couple weeks ago, I was getting accurate repeatable results that were within 10 ppm of ICP testing. I always use 0 TDS RODI for the testing and cleaning of the vials. I may try a more accurate syringe....that might help. Thanks!

FWIW, with the Hanna calcium kit, 0 ppm TDS water may not be sufficiently low in calcium. It is freakishly sensitive to low levels of calcium since it multiplies them by a factor of 100 in the blank.