I run carbon and vodka dose and I never see my alk drop because of it. I do my weekly water changes and my alk stays the same. I wish they would have elaborated on that more.
What they are saying Is If you are running a low nutrient system you need to keep your alk.at 7-8 dkh. That means if you are carbon dosing you are probably doing a low nutrient system.
One of the many wrinkles with carbon-dosing. (Nothing indicates this effect is related to nutrient levels...it's the carbon dosing.)
The cool part is that NOBODY really understands why this happens...follow me here...
I suspect that excessive levels of carbonic acid in the water mess with the test kits we use (which all assume "normal" sea water conditions, especially pH). If so, the folks with lowered pH or alk may not actually have the alk/pH their kits indicate. With acidic water, kits should in theory read low because the color-transition would be too soon (or too intense)...and if you follow your kit like a good reefer, this will cause you to dose more to compensate. Since your water is normal (just the kit is malfunctioning), you actually overdose.