Salifert Ca+ Test Question

[LongShot]

This may be dumb, but when using the Salifert Ca+ test kit, it's hard to determine the titration end point with the kind of accuracy I'd like. I know you're looking for a change from hot pink to clear blue, but do you stop at the very first appearance of that blue or do you continue until it stays blue? If I stop right at the initial appearance of the blue color, the test solution changes back to a sort of magenta/purple after about 15 seconds. It generally takes 2 - 5 more drops of the Ca-3 reagent to achieve a relatively persistent blue. So where is the end-point really?

I had the same experience way back when I was using the Sea-Chem Ca+ test kit when it first came out, and arbitrarily decided that if the blue persisted more or less unchanged for 15 seconds, that was the end-point.

FWIW, it makes the difference between a Ca+ of 380 ppm and 410 ppm, either of which seems to be acceptable to my tank's inhabitants. 'Course I'd be happier with the latter, but....

[kram138]

IMO you are going to want to go with the result at the first sign of a color change. I use a Salifert cacium test as well. The same thing happens to me but it usually takes only one more drop to get the blue to stick. I record the result when the blue first appears. I usually get 420-440.

It's nice to see another fellow Cali Reefer.

[DennisW]

Well....it all depends. If you LIKE the value when it immediatly turns blue then......GREAT. If you like the value after adding a few more drops than.....thats the one to believe!

Just kidding! I would trust the initial color change like kram suggested.

Dennis

[LongShot]

Mark,

First appearance of blue is as good a place to stop as any, I guess. I suspect that so long as I stick to one point or another consistently, I'll be fine.

I made a dumb mistake in the way I set up my kalk dosing, and it was dispensing a lot of calcium carbonate precipitate, which naturally drove the pH up and the Ca+ down. My first clue was what looked like a small calcite mine developing in the sump where the kalk dripped in. Anyway, once the sump was cleaned up and I started dosing kalk properly, a good big water change was all that was needed to get things back on course. So I'm hoping to see Ca+ levels in excess of 400 regularly.

BTW, I'm in the East S.F. Bay area of Ca.

Regards,
Bert

[kram138]

Originally posted by LongShot
I made a dumb mistake in the way I set up my kalk dosing, and it was dispensing a lot of calcium carbonate precipitate, which naturally drove the pH up and the Ca+ down.

What exactly was the mistake you made? I'm just asking so none of make it. We love learning from OTHER peoples mistakes. lol

[LongShot]

Well, it's a bit embarrassing, but....

I thought I'd try to mimic the action of a kalk reactor by putting a small powerehead in my kalk reservior and connecting it to a timer set to run the PH for a few minutes every so many hours. Sounded like a good idea at the time , but instead of keeping the kalk saturated, what it did was keep the usual calcium carbonate precipitate suspended in solution. Not a good thing....

At any rate, I figured out the error of my ways before the pH went above 8.47 and the Ca+ fell below 335, so no major harm done. None the less, pulling the sump and getting all the "crusties" out of it was not a task for the faint of heart.

I've gone back to the traditional method for mixing and dosing kalk, and Ca+ and Alk. are much better. If & when that becomes too much of a bother, trust me, I will spend the $$ on a REAL kalk reactor

Regards,
Bert