low Alkalinity in new salt mix

[Jason Scalise]

Hello,
I have been using HW-MARINEMIX salt in my NSW reservoir and after mixing and testing (tested with different kits multiple times) the NSW mix measured 4.5 Alkalinity.

My alk in my tank has been consistent for months around 8.5
I recently cut down the frequency of water changes from 1g/day to .5g/day. Just at that point I noticed alkalinity in my tank creeping up and my SPS bleaching after about 2 weeks.
I measured alk today and it was 9.2.
I also dose alkalinity and calcium (with a doser pump) ESV-1 and 2 and that has been steady.

All other parameters are normal. (triple checked). lights are fairly low intensity at the moment too.
many other corals look fine.

if my NSW had very low alk and I reduced the input from the NSW, that would explain the rise tank alkalinity.

the question is however, has anyhow heard of this high quality salt mix having SUCH low alkalinity?? its half of what is advertised?
it seems SO low. but it would fit this picture.

 

[Mastiffsrule]

Evening

I found on BRs it should be mixing to 9 at 1.024. My first thought is test on the new mix. Could you mention what your Sg is.

If it is a smaller tank I would think the change in maintenance may call for an adjustment in dosing. I’ve not run smaller tanks so I hope maybe someone with a bit more experience dosing stops by

 

[Jason Scalise]

Evening

I found on BRs it should be mixing to 9 at 1.024. My first thought is test on the new mix. Could you mention what your Sg is.

If it is a smaller tank I would think the change in maintenance may call for an adjustment in dosing. I’ve not run smaller tanks so I hope maybe someone with a bit more experience dosing stops by

thanks.
Should've mentioned.
SG of the NSW in the reservoir is 1.026
tank total capacity is 112gallons.

I agree and found the same info on BRS. that is why I was so confused as to why it mixed with an alk of half that (4.5 instead of 9)

 

[spidercrab]

Wow that is definitely defective product at that low.

 

[madweazl]

Have you double checked your salinity? An instant change of .7dKh wouldnt cause problems with the corals so a gradual one certainly wouldnt. A low salinity sure could though.

 

[Jason Scalise]

thanks.
yes, I have checked all other parameters. salinity has been stable I the 1.026SG range. temp stable. lights stable. etc.
Agree that .7 dKh is not a massive change.
I am mystified on this end too.
but hence the question as I could account for a salt mix of 4.5 dkH.
I am not saying it was alk per se....but frustrated that it the source of the problem seems elusive thus far.
I have added some bicarb to the NSW reservoir and that has brought it up in the 8.5-9 range reliably.
will keep searching.
something has upset the corals however...

 

[Jason Scalise]

I would say that the bleaching of the acroporas was on the undersurface...meaning not the tips that are most exposed to light. Sort of bleaching in their shaded parts.
that made me thing it was a more systemic issue and not due to light intensity.
I did reduce my light intensity recently so I suppose it could be due to LACK of light but would have not expected true bleaching per se.

 

[Randy Holmes-Farley]

I’m not sure where the issue lies (testing vs defective product), but it is important to figure out. The salt mix is easy to fix with baking soda if the alk is the only issue in it, but it might not be.

 

[madweazl]

thanks.
yes, I have checked all other parameters. salinity has been stable I the 1.026SG range. temp stable. lights stable. etc.
Agree that .7 dKh is not a massive change.
I am mystified on this end too.
but hence the question as I could account for a salt mix of 4.5 dkH.
I am not saying it was alk per se....but frustrated that it the source of the problem seems elusive thus far.
I have added some bicarb to the NSW reservoir and that has brought it up in the 8.5-9 range reliably.
will keep searching.
something has upset the corals however...

Have you checked the salinity with another device?

 

[Jason Scalise]

Have you checked the salinity with another device?

yes. thanks.
I have tested different with salinity probes that all matched.
and also took sample to LFS for them to verify.