Raising pH in saltwater to 9-9.4 with sodium bicarbonate

[sagcali]

I have been trying to raise the pH of sand filtered salt water. I tried sodium bicarb but have been getting a thick precipitate. I am trying to raise the pH to 9-9.4 It starts out at around 8.2.
I have also tried NaOH and have had no luck maintaining the pH at 9-9.4

Any advice would be much appreciated.

 

[symbolipoint]

For just raising the pH, use of NaOH should be able to bring it to 12 with no problem.

What was the source of your sand filtered salt water? How was it treated before you found it and how else did you treat it before adding the alkaline materials to raise the pH?

 

[sagcali]

The saltwater is from an underground SW source on Oahu, HI.

 

[sagcali]

I'm using the water to culture micro algae.

 

[chemisttree]

Add Kalkwasser or limewater. This will also add calcium to your water which might be depleted in the water. You might try testing total alkalinity before trying it though. I would avoid adding NaOH if you are trying to duplicate what is present in seawater or if your microalgae is intended to grow on or with coral. NaOH will precipitate any remaining Ca that might be present.