2 Part Question

[Chameleon]

Hey yall,
I am using two part to keep my alk and calc levels where they should be. I know all the chemistry forums say to use both in equal ratios to keep the right concentrations of competing ions in the water, however my alk seems to fall much faster than the calc. Should I bump up the alk or should I keep with dosing equal amounts? I'm also planning to start using kalk in my autotopoff as my calc and alk use levels have really gone up lately (yay lots of growth).
Thanks for any help
-Cham

[BillyC]

Go ahead and bump up that ALK dosing.

[Chameleon]

is this the general consensus?

[Kbra]

I tend to dose around 2:1 alk:Cal ratio. Bump up the alk

[dsmhero]

Yes just bump up the alk dosing for the time being.

[dsmhero]

BTW here is a fantastic article relating to this subject.

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com

[Paul_N]

When I first dosed with 2-part I did the equal parts thing and then kept testing and then adjusted. Just keeping testing and adjusting as needed.

[robert]

I don't pretend to know as much on this subject as Randy Holmes-Farley but I do find fault with his article. His conclusion is predicated on the contention that "When this nitrate proceeds further along the nitrogen cycle, depleted alkalinity is returned in exactly the amount lost". Here he only considers the heterotrophic consumption of nitrate in anoxic conditions - assuming a ready supply of dissolved organic carbon. (in his equation glucose). This might be true if one is running a the style of denitrator which requires feeding - (typically sugar or alcohol) however in the absence of carbon augmentation this process does not proceed very far.

I think a more typical denitrification process which occurs naturally in deep sand beds (and to a certain extent without a DSB) and requires no feeding - one which proceeds naturally in depleted carbon environments - is the mixotrophic sulphate mediated denitrification where 2 moles of H+ (acid) is produced for every 8 moles of nitrate consumed. Alkalinity is consumed - not released. The lower ph produced is somewhat buffered by substrate liberating ca which in turn further unbalances the ALK/CA equation.

So it is my humble opinion that on this one - Randy has missed the mark for the majority of aquariums.