How to switch between two brand of alkalinity

[TELEMESH REEF]

Hi guys im using RedSea foundation components A,B,C( alk,cal,mg). Due to cost im thinking of using another brand. There is still little left in a acrylic container should i just add another brand of alkalinity or just empty the container before adding new one

 

[windemerejack]

I would just empty it, the new stuff might be a different strength or composition.
I dont think there would be any harm in mixing it if its only a tiny amount, but its no big deal just to empty it.