ALK refuses to go up above 8 DKH

In my 55g tank, my mag is at 1450-1500. My cal is at 440. PH 8.3. ALK at 8 DKH.

I been adding 25ml (5 caps) of Seachem Reef Carbonate for 3 days in a row now and testing the next morning. It just refuses to go higher than 8. Cal and mag remain at 440/1500.

I used 2 separate CAL and ALK test kids (1 set of API and 1 set of Red Sea), same results.

Any ideas?

P.S. I used the same carbonate bottle to get it from 5 to 8 DKH earlier with no problem.

 

As your Magnesium is utilized and lowers, you'll have more room for Carbonate and Bi-Carbonate ions. Also, what is your salinity/specific gravity?

 

1.025

Should I stop adding carbonate until my mag lowers then? Or continue to try adding it once a day unless Calc gets depleted?

 

what salt r u using???

 

Instant Ocean Reef Crystals

My last water change (20%) was a week ago. And ATO has no salt in it.

 

On your next waterchange, mix it to 1.026 and that will allow your Alk to to up to 9 (maybe 10). However, right now what is happening is when you add the Reef Carbonate, it's just precipitating out (and will continue doing so unless you increase salinity or lower Magnesium). At 1.025, you are likely fully saturated.

 

i always had problems with reef crystals.. it was always something different it seemed like every week... i switched to coralife a while ago and had very stable numbers... maybe look into changing your salt next batch... rather than dosing things to get your water back right..i would rather just do a water change to fix something...

 

Thanks fellas.

That could also explain the dust like residue on my rocks from below thread:
http://www.3reef.com/forums/live-rock/need-help-detritus-rock-109128.html

I think i'll stop dosing unless it drops to <= 7 and will try Tropic Marin Pro-Reef next time.