Baking soda and pH

[Bojan]

I have used Natriumhydrogencarbonat NaHC03 for KH dossing but because I had idea to increase pH, I bought baking soda Na2CO3.

Yestarday I start dosing Na2CO3.

NaHC03 pH = 8,05 -8,29
Na2CO3 pH = 8,20 -8,45

Increase of pH is quite high 0,15.

http://www.sloreef.com/phpBB2/download/file.php?id=1200

4 years ago I baked NaHC03 by myself 1 hour 150C, but according to my memory increse of pH was not so high.
Do you have idea , what can be different between my DIY Na2CO3 and bought Na2CO3 ?

I will start dossing Na2CO3 only during night to improve pH graph.

[Randy Holmes-Farley]

You may not have fully converted it to Na2CO3.

Also, the higher the alkalinity and the higher the starting pH, the lower will be the boost on adding Na2CO3.

In my tests, adding 1.4 dKH with Na2CO3 boosted pH by about 0.34 pH units. :)

[Bojan]

I mixed Fauna Marin ULtra Trace jodite and flouride, i believe KJ and NaF with NaHCO3 sollution (based on instructions). Is it possible that can not be mixed with Na2CO3 and I have to dose separatelly ?