Dosing

[Delphinus]

I voted 3-part but IMO realistically 2-part and 3-part are the same thing. Big 3 being Ca, Alk and Mg .. you don't really have to dose Mg on a daily basis (or if you do it's some tiny amount compared to the other two). If you dose 2-part with something like Seachem "Reef Builder" and "Reef Advantage" (I forget which one is Ca and which one is Alk but that's what they are together), then you are already dosing Mg anyhow. If you use the Randy Holmes-Farley recipes then you have to dose Mg separately.

I dunno, Ca reactors still have their place but you said it yourself, you can't beat the simplicity of 2-part. (No CO2, no "dialing it in", no fussy regulators, etc.)