2 part dosing.

[Richard972]

Best 2 part dosing for 29 gallon biocube? Mixed tank but heavy SPS. Do weekly water changes but noticing that my alkalinity is dropping over the week. As the coral grows I will have more issues.

 

[laverda]

B-ionic is the simplest as you just fill the gallon jugs it comes in the rest of the way with RO/DI water. If I remember correctly the smaller bottles do not even require you to do that. It just gets pricey on larger tanks.
Personally I bake backing soda for ALK, have dry calcium chloride for Ca and Magnesium sulfate and Chloride for Mag. All come as powder or pellets that I mix with RO/DI per Randy’s recipes.

 

[PatW]

I use BRS two part. They use soda ash for ALK, Calcium Chloride for calcium and Mg Sulfate and Mg Chloride for magnesium.

For your system enough to mix a gallon of ALK and Ca should last quite awhile unless you have a really high demand system. I use a salt mix with a Mg of 1350 and water changes keep Mg stable. Corals use Mg but not much and you could very well get by without it.