Calcium will not drop?

[demariners]

So I noticed the other day that my nutrients were pretty much 0 for Phos and Nitrate. I tested today and the same thing. I noticed that my clam died and my colors are starting to bleach a bit. Specially the SPS. I am told that I have a ULN system and I need to have a lower Alk and Calcium and dose Amino acids. With all this being said my ALK yesterday was 10.9 DKH and my Ca was 480ppm. My mag was 1480ppm. So all elevated levels. I am changing my salt as well as I am sure that was a contributing factor.

The issue I have is I turned off all my dosers completely yesterday. Today at the same time my ALK is 9.4 but my Calcium is still at 480ppm. I did the test a few times to make sure. How is this possible? Is there some ways I can slowly decrease both of these levels? Possibly a water change with lower ALK/CA/MAG?

Thank you for any assistance.

[LobsterOfJustice]

Calcium is used up much slower than alk. It may take a while to drop, especially if your corals are stressed and therefore not actively growing.


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[Rafty]

Why are you wanting to drop these levels. My understanding is they are exactly where you want them.


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[demariners]

I have a ULNS. Unintentionally I might add. Therefore running levels much lower then normal is best.

[Rafty]

Excuse my ignorance but what is a ULNS?


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[demariners]

Ultra Low Nutrient.

Most days my Nitrate is 0-.25. I have difficulty raising it. My tank has been like this for years.

[bertoni]

I am not sure that your tank will have a problem, but some people report issues with alkalinity much over 8 dKH or so when running carbon dosing or the like. I have never heard of a problem with calcium, but if you want to lower it, the consumption rate is 20 ppm of calcium per 2.8 dKH consumed, so it might take a while to drop much, especially if the tank gets water changes with a high-calcium salt product.

[demariners]

Well, my corals have begun to bleach so I started Amino Acid dosing a little more heavy to combat it. However, I noticed while doing so my ALK was 10.9 and Calcium around 480. So I assumed I was starving them. So getting it lower I think would be best. Eitherway what was odd is the ALK dropped 1.5 in a day and Ca remained at 480. Was wondering if I should just continue to not dose and let the levels drop. As for my salt I have not done a water change yet but I use Red Sea Blue Bucket now.

[dkeller_nc]

You're correct that high alkalinity and calcium levels, combined with very low nutrients and high intensity lighting is indeed a recipe for bleaching.

From the standpoint of calcium and alkalinity in tank water, there's quite a number of legit reasons that your measured calcium level isn't dropping in step with the alkalinity. Alkalinity is also a player in the nitrate cycle, not just coral calcification. So it can easily be consumed in unequal molar ratios to the calcium.

And there's another aspect; most drop-type titration tests aren't terribly precise. 20ppm is about the limit of quantitation with the hobbyist tests, so your calcium level could actually be dropping somewhat without it actually showing up on the test.

[bertoni]

Either way what was odd is the ALK dropped 1.5 in a day and Ca remained at 480.
1.5 dKH corresponds to about 10 ppm of calcium, which probably is within the noise limits of your kit.