Calcium Conundrum

[Bore-Punch]

on the lamotte titration, i would get it to its end point then as i go to write the results down by the time the i look up its back to purple and not quite at end point. the API kit just never reached the end point at all ....although i let it settle for 2 hours in frustration and when i came back it was blue....that was with 1000ppm Ca worth of titrate. would precipitated calcium be causing this...my early on ph was 7.79 its now a steady 8.15 at night and 8.30 during the day (huge diatom bloom, which is to be expected considering my lack of filtration and new set up)

i did a 60 gallon water change last night, still havnt gotten around to re-testing, work has been keeping me busy. ill update results when i get a chance.

 

[Habib]

Yes, as already mentioned in my previous post precipitated calcium particles can cause the continious reverting of color.

But it could also be the reagents.

Did you try measuring water change water?

If that too gives similar color change or lack of then it might be worthwile to use a friends kit or buy a different brand kit.

 

[incognitus]

that was with 1000ppm Ca worth of titrate

For me 1000 ppm it´s not possible even if precipitated. I think pH during test is not right and so indicator is not blue to the end of calcium. You get enough pH with titration reagent for a while, but with little CO2 pH lows and red returns.

I would try to use 10 drops of sodium hydroxide in Lamotte test instead of 6. With API 8 drops of reagent 1 instead of 5. This way pH can be right in your test.