Ca Testing question
 

When testing the calcium level with the salifert kit, i have read some poeple take the measurement at the first sign of a color change and don't finish as the direction say to(wait for the "clear" blue color... Now the first color change i get is a deep cluish color and that reading would be 400. Where as if i wait for the lighter blue it is more around 500... Too much of a difference for me to be comfortible without asking for other opinions... LMK what you think so i can figure out what i need to do... To answer a question before it is asked i do keep sps and lps with some softies....

i've often wondered the same thing... tagging along

same here always wondered if I was doing it right

I know for the salifert alk test the same question was asked to the guy from salifert by a friend of mine. He said that instead of waiting for the pink color to appear, you should take the reading at the first sign of color change. The liquid will change from a blue to an almost greyish color. This is when I take my reading. One more drop will make the solution pink and I will take the two readings and average them.

I saw a thread regarding that which is why i am asking if it is like that for all salifert tests or just the alk? To me this is alot of play between the two color changes for the calicium and just to average it seems kind of like a shot in the dark to me.... I also read that the salifert forum isn't responding to anything currently, not sure why but that is why i am posting here.. Just to find out what everyone else is doing and thinking with this

I just checked again and actually don't even see a salifert forum at all anymore.... I might just be temporarily blind but i don't see it, is it just me?

This applies to all titration based test kits. Chris (acidraindrps) is right. What we are essentially doing with these tests is binding a chemical and a dye to all of that which we are trying to test. The last step (with the syringe) is a dropwise addition of another chemical which bonds to the compound we created and changes its color. However the initial dye is stronger than the final chemical (syringe) so it's color remains until ALL the calcium/alkalinity/magnesium/whaterver is bound up. At the saturation point the solution will usually turn grey, or some other intermediate color. That reading is your true reading. Once the color change is complete, you've technically added just a little too much of the solution, thus giving you a slightly high reading (usually one drop too high).

Translation. If you can catch that interim color change, do so. That is your EXACT reading. If you overshoot by one drop and get a complete color change, its still probably close enough :). This applies to Salifert Calcium, Alkalinity, and Magnesium for sure. Although I hear their Alk test kit is chaning soon...

Thank you for the clarification and explanation... Makes everything a little easier instead of guessing and hoping you are taking the right reading... Anyone know why salifert no longer has a forum, i think it would have been easier and quicker to ask them and have them clarify

The alk test kit actually is already changed. There is a new method for testing, and to my knowledge it is a little more time consuming.

SkiFletch, Great explaination. Thanks

Regarding Salifert, There were a number of complaints about alkalinity test kits and some others.Salifert stopped responding and eventually dissappeared off the board.