What would cause a rapid drop in Calcium?

[VashonBigs]

I am dosing 2 part through Apex Trident on a 150 gallons total water volume. It’s adding maybe 120 ml per day. The only difference is I added a little Kass to the ATO yesterday. Insane drop in Calcium levels. Checked with another kit that is reading about 300.

 

[Miller535]

A little more info may be helpful. How long the tank has been running. Sps tank? Mixed? And what is Kass?

 

[VashonBigs]

Kasswasser to maintain PH and Calcium outside of the two part.

tank running for 6 months but some of rock and sand from a well established tank I am shutting down. Mixed reef. Maybe 5 large LPS, 3 med/large SPS, probably about 15 growing frags, primarily SPS. A softy or two. Coral and fish are doing great but I have maintained Calium around 420 until this rapid drop.

 

[JoshO]

That's a huge drop. Do you ever see even remotely similar swings?

 

[VashonBigs]

That's a huge drop. Do you ever see even remotely similar swings?

Never... first time.

 

[((FORDTECH))]

2 questions did you just do a water change ? And what is the % level left in your Regents ?

 

[Pntbll687]

Check if you're low on reagents. And I would definitely test with a 2nd kit.

 

[Miller535]

Kasswasser to maintain PH and Calcium outside of the two part.

tank running for 6 months but some of rock and sand from a well established tank I am shutting down. Mixed reef. Maybe 5 large LPS, 3 med/large SPS, probably about 15 growing frags, primarily SPS. A softy or two. Coral and fish are doing great but I have maintained Calium around 420 until this rapid drop.

I think you mean Kalkwasser.

Have you verified the drop with hanna, or some kit? Or just going off of the trident?

 

[Rybren]

Unless you had a massive precipitation event, I can think of no process that will cause a calcium drop like that. Ca will only drop 18-20ppm for each 2.8dKH of alk used, so it is highly unlikely that the drop is correct.

IMHO, either the levels were actually lower than what you were reading to begin with, or the current readings are incorrect. I suspect the latter.

 

[VashonBigs]

2 questions did you just do a water change ? And what is the % level left in your Regents ?

I did change 15%. I guess I should check my salt mix but I did check the salinity and it was fine. Really strange...

 

[JoshO]

Have you got any other test kits to compare the results to?

 

[Randy Holmes-Farley]

Never... first time.

Test error, most likely.

As Rybren noted, Calcium cannot suffer big drops without huge alk drops, about 2.8 dKH for each 18-20ppm of calcium decline.

 

[blasterman]

What Randy said.

ALK levels have many factors that can cause it to shift violently in short time periods.

Calcium - nope. The amount of dissolved calcium in a reef tank, unlike alkalinity, is pretty substantial, and it cant just go away. You need to precipitate it typically by driving alk over 15 dKH or your test is bad.