Alkalinity

[Seriak]

So my tank is a couple months old now and I have done a 15% water change every week for the last month. I finally got around to measuring my alk and Ca. My Ca was between 400 and 450. (I didn't bother with the precision test) My ph is 7.8-7.9, but my alk is in the 3.5 dkh range. I did the test twice using my Hanna kit. Now does that alk seem plausible or should I buy a different test kit and test again before I go dosing anything.

[Aquattro]

Ya, it sounds plausible. I'd maybe retest with a different kit, but depending on salt and source water, it could be that low.

[coolhandgoose]

Are you sure the measurement is in dkh or in meq/l (I think that's what the other one is called)

[Aquattro]

Are you sure the measurement is in dkh or in meq/l (I think that's what the other one is called)

good point. I think that value is fine for dKh...too many units for alk :)

[coolhandgoose]

Other way around, that's really low for dkh. :mrgreen:
If its meq/l I think it's fine.

[Seriak]

It was 62 then 66 ppm.

[Delphinus]

Yeah that's really low. What salt are you using?

[Seriak]

I initially used a half bucket of 8 year old IO and the rest has been new reef crystals.

[Delphinus]

Weird.

Are you dosing yet? I'd start by dosing Alk for now to bring that up to targets .. The Hanna's measure in mg/L CaCO3 which convert to dKH or meq/L as follows ..

The instrument directly displays the concentration of alkalinity in ppm of CaCO3. Alkalinity conversion:
1 ppm CaCO3/L = 0.02 meq/L
1 ppm CaCO3/L = 0.056 dkH

There's also this: http://glassbox-design.com/2009/alkalinity-conversion/

.. So I think you want to target your Hanna readings to be in the 150-160ish ballpark. I think..