Question about hardness test

[waterbear]

the other factor, as I stated in an earlier post, is to swirl the test vial for 30 seconds between drops of the titrant and to really give it a good swirl (up to a minute) when you add the indicator (reagent 2). The ideal way would be to use a magnetic stirrer and a beaker when you do the titration like some of the pool stores do. This test can take a while to do if you do it right. Rushing it can cause all kinds of problems (a lesson I learned from my years of keeping saltwater reef tanks!)
Also, reagent 1 is what removed the magnesium interference so make sure the 20 drops are well mixed before adding the indicator!