General test kit questions and interpreting results from Salifert & Red Sea

[Reefinmike]

Hey all, I've gotten back into the hobby full bore this year and I learned how terrible those API kits are as well as the importance of quality test kits and a way to verify those kits. I started my tank back up 4 months ago and have since done two water changes. none of those water changes happened between data shown below. I started with a bad batch of instant ocean( mag 1600+, cal 550+) and up until recently I have only dosed sodium carbonate. Recently I did add 20ppm worth of calcium chloride and started dosing kalk a few days ago. I test my water a LOT in an attempt to get a good pulse on my tank's usage before starting automated dosing of kalkwasser. I test alk 1-2x a day and calcium and magnesium every 3-4ish days. I test my alk using the red sea test as well as the hanna dkh checker. When I don't dose any alk, it seems my tank uses .3dkh worth per day. When dosing, I would dose .5-.7 a day to keep the alkalinity stable. I wonder if the funky calcium and magnesium results could be from things precipitating out? I have calcium and magnesium test kits from salifert and red sea. I have a general idea where my levels sit but I'm not seeing much consistency between tests.

I follow the test instructions to the T. reagents are never mixed and the vials, syringes and tips are always washed, scrubbed and rinsed in RO/DI after use. I wash the glass red sea vials with diluted muriatic acid after calcium and magnesium tests. they seem to leave a precipitate. My red sea calcium and magnesium titrants have stuff floating around in them, is this normal? I always give them a gentle shake or swirl before using. The particles were in there when I opened the kit. Also, the red sea calcium kit will change to blue then slowly back to pink over 7-15 seconds. it seems to take an additional 4-5 drops after the first color change to keep the color stable. Is this common? I believe the directions just say to wait a few seconds.

Any idea what's going on here? or is this just the kind of consistency I should expect from these hobby grade kits?

 

[Scotty Buttons]

Are the test kits expired? We're they exposed to high heat or freezing conditions?

 

[Reefinmike]

not that I know of, they were all purchased from brs this spring/early summer and packages are never left outside. the salifert tests have a 2021 and 2023 expiration and the red sea 2020.

 

[infinite0180]

FWIW my RS Cal and Mag titrants both have some precipitation floating in them and have from the day i opened them as well. Also, when i titrate anything (whether it be at work or at home for my tank) i add titrant until the color change persists for 30 seconds. So what that means is when i get close to the endpoint i add titrant dropwise while swirling until the color change remains for roughly 30 sec. Just go slow when you get close to the endpoint and continue to add and swirl till the color change holds...

 

[Randy Holmes-Farley]

The Red Sea magnesium kit gives many people problems and I'd generally avoid it. The magnesium changes you are seeing are test error. Real magnesium depletion is about 0-2 ppm per day or so, and it never rises on its own

Precipitation would not, explain any issues you are having, at least as I understand what you are saying. It takes out about 2.8 dKH of alk for each 18-20 ppm of calcium and about 1 ppm of magnesium.

 

[Reefinmike]

Thanks for the input Randy, I was always under the impression that all red sea tests are pretty reliable. I’ll gladly take the red sea magnesium test out of my routine testing. I like the color change but the test takes longer than salifert. I do run my alk high and I suspect that a good portion of what i dose precipitates out. It seems the more I dose, the less effective the dose is. For example if I don’t dose for three days and start at 11dkh I will see the alk drop about 1DKH or .33/ day. If I dose .5dkh a day the alk will usually test the same 24hrs later. If I add 1dkh a day the alk will be .2-.3 higher 24 hours later. I’m not too worried about it, I was only concerned it was causing the funky magnesium results.

Thanks infinate0180, it’s reassuring to hear im not the only one with particles in my titrants. Sounds like i’ve been interpreting the color change endpoint the right way.



One more question for anyone who has the salifert calcium test. Does your ca-2 reagent waste 2-3 drops as you turn it upside down? I’m nearly out of ca-2 and there is a good 50%+ more titrant in the bottle. I always disposed of any extra titrant at the end of the test. I feel the poor dropper bottle design is giving me 25% fewer tests.