Alkalinity drop in new saltwater

[puffy127]

I've been maintaining around 167 ppm (9.3 dkH) alk in my DT. My newly mixed RC saltwater is low at 115 ppm (6.44 dkH) so I added baked baking soda to it to try to match my DT. According to the reef calculator, for 22 gallons, I added 1 tsp of baked baking soda. After mixing for 1 day, I checked and it only raised it to 119 (6.6 dkH). I dosed another tsp, mixed for a day and it came up only a little bit, to 126 (7.06 dkh). Thinking maybe my baked baking soda went bad, I dosed 1.2 tsp of baking soda and it brought it up to close to what the reef calculator calculated for baking soda, 170 ppm (9.5 dkh). After a day, it has dropped down to 141 ppm (7.9 dkh). What is going on? Why did my alk drop in my sw mixing container?

 

[Randy Holmes-Farley]

Assuming the additions and measurements are correct, you are precipitating calcium carbonate. Heat in the water, as well as higher alk and higher p[h all contribute to such precipitation.

If you want to boost the alk of new salt water, use just baking soda (not baked), stir it only briefly, and don't heat the water. :)

 

[puffy127]

Thanks Randy. My saltwater mixing station is in my garage where it gets over 90 degrees and a mixing pump on all the time. I will turn the pump on only when needed to mix and will try to bring the water inside to cool off before dosing and/or doing wcs.

 

[Randy Holmes-Farley]

You're welcome.

Good luck!