disaster strikes!!

[untamed]

Originally Posted by sharelove

...when I added it on Monday, it was still cloudy. Just before the water change I had done all my tests, everything was in order. Alk was a bit low at 2.7.....

.... I took an alk reading on thursday and it was a lot higher: 5.8 .

That's the part that struck me. Still cloudy sounds like super high Alk content. I suspect the SW or mistake on the additive caused a dramatic pH swing.

I dug out my Holmes/Farley info on the Alk/pH relationship. At equilibrium in normal SW, there is a set relationship between Alk and pH. Using this relationship as a starting guide, that Alk reading of 5.8 is right off his chart, but might equate to a pH of 8.6. Given that the system spent a few days re-equalizing, I bet it was a lot worse than that had you measured it immediately following the water change.