Alkalinity and Salinity Relationship?

[AKL1950]

I had been a bit delinquent in recalibrating my trident salinity probe, Hanna salinity probe and refractometer. Once I did it, I realized they were all off and my water was running about 37.4 salinity Instead of 35 where I wanted it. I started gradually bringing it down to 35 over about 10 days. What I’ve noticed since doing that is my Alkalinity has risen from 8.0 up to 8.4, Ca has dropped from 450 to 390 and Mag has dropped from 1470 to 1390 very quickly after I made the adjustment.

Is there a tight relationship between salinity level and the three Alk, Ca and Mag causing this, or would correcting my salinity make it so consumption of the other three to start changing so quickly? I’m not trying to chase numbers, but to see such a quick change in everything worries me.

I do auto water change daily (2 gal/day for total water volume is about 180 gal), dose 30ml Alk, 30ml Ca and 10ml Mag daily. Tank is SPS dominate.

PH 8.1-8.3, temp 79-80, NO3 14.5, PO4 varies 0.1-0.2

 

[Pistondog]

When you dilute saltwater, you also dilute all elements in the saltwater.

 

[Bonsai reef]

A possible explanation of the alk increase could be that your corals didn’t like the change and as a result consumption of alk has dropped? are you are doing alk as per previous consumption rate? Cuz alk is the only notable change of the three due to dosing in a short period over the other two.

 

[AKL1950]

When you dilute saltwater, you also dilute all elements in the saltwater.

Okay, I can see that, but Alkalinity has been going up since then. I guess that could be attributed to the salt mix. I use IO Reef crystals. When I make new saltwater, I do 50 gallons at a time. It’s in a 75 gallon reservoir. I guess the Alkalinity change could be a result of variations in the salt mix.

 

[Pistondog]

Test accuracy may also come into play.
Hanna alk test is +/- 0.3 dkh.

 

[Bonsai reef]

Okay, I can see that, but Alkalinity has been going up since then. I guess that could be attributed to the salt mix. I use IO Reef crystals. When I make new saltwater, I do 50 gallons at a time. It’s in a 75 gallon reservoir. I guess the Alkalinity change could be a result of variations in the salt mix.

Testing your new salt mix can confirm this

 

[AKL1950]

A possible explanation of the alk increase could be that your corals didn’t like the change and as a result consumption of alk has dropped? are you are doing alk as per previous consumption rate? Cuz alk is the only notable change of the three due to dosing in a short period over the other two.

That makes sense. I was seeing increased growth rate before I made the adjustment, and then those really fast growers seem to have slowed down. That added to my confusion of why Alk started going up while Ca and Mag started going down.

 

[AKL1950]

Test accuracy may also come into play.
Hanna alk test is +/- 0.3 dkh.

I use trident, Salifert and Hanna to test Alk. Trident seems low, Hanna seems high and Salifert is in the middle. I tend to just average the three and use that for a number. This week, trident says 7.85, Salifert 8.2 and Hanna 8.8. They are always in sync with the spread, but they are all trending up now.

 

[AKL1950]

Testing your new salt mix can confirm this

Lol! It will test between 11.0 and 12.0 right after making new saltwater. That’s reef crystals. Even so, that tank usually stays close to 8.0-8.1, but now rising every week. That’s why I’m looking for a cause.

 

[Bonsai reef]

That makes sense. I was seeing increased growth rate before I made the adjustment, and then those really fast growers seem to have slowed down. That added to my confusion of why Alk started going up while Ca and Mag started going down.

We all know corals hate changes. Good to bad or bad to good does not matter.

 

[Bonsai reef]

Lol! It will test between 11.0 and 12.0 right after making new saltwater. That’s reef crystals. Even so, that tank usually stays close to 8.0-8.1, but now rising every week. That’s why I’m looking for a cause.

Then I would immediately adjust my dosing based on current consumption. Your high alk salt + dosing was equal to your past consumed. Now the consumption may have dropped, and you water change is adding to the alk and dosing on top would surely increase your alk. Other two may have dropped due to salinity correction. If they keep dropping even after then check your salt mix.

 

[AKL1950]

Then I would immediately adjust my dosing based on current consumption. Your high alk salt + dosing was equal to your past consumed. Now the consumption may have dropped, and you water change is adding to the alk and dosing on top would surely increase your alk. Other two may have dropped due to salinity correction. If they keep dropping even after then check your salt mix.

Sounds good. I’m fairly new and still learning. Now that my Acro load is getting higher I’m seeing a lot of moving parts I’m not used to. Testing has always been once a week, but I’m moving to everyday till I can get my stability back. Thanks for the help.

 

[Bonsai reef]

Sounds good. I’m fairly new and still learning. Now that my Acro load is getting higher I’m seeing a lot of moving parts I’m not used to. Testing has always been once a week, but I’m moving to everyday till I can get my stability back. Thanks for the help.

Sounds like a plan. We are all learning