Calcium drop 100 ppm in 48 hrs??

[tigresteve09]

Looking for feedback on how these parameters interact, if this makes sense, is ok and what I should start doing to stabilize. My take has been running for about 2 months. I started with mature bio media so it cycled pretty quick. My tank is a 32G AIO.

I tested two days for the following results.

My most recent test is below. The alkalinity rose, and calcium dropped 100 ppm. I used a salifert test and thought it had to be wrong so followed up with a Hannah test and confirmed it’s correct.


I’ve been dosing magnesium almost daily trying to get it up to 1350-1400 but it’s not really rising. I also dose Brightwell code A&B but don’t do it often because I don’t understand exactly how it works.

 

[rishma]

A 100 ppm drop would correspond to a 14 dKH drop so the calcium value change is due to test error.

In a reef tank, for each 2.8 dKH alkalinity consumed, 18-20 ppm calcium and 1-2 ppm magnesium are consumed. You can use these ratios in a variety of ways. I recommend basing everything off alkalinity because the tests are generally accurate and repeatable.

Magnesium test kits are so error prone that I don’t own a test kit anymore. I follow Randy’s Magnesium Method and just dose 1-2 ppm magnesium for every 20 ppm calcium I dose. Periodic ICP shows this keeps it on target.

Hope that helps.

 

[Sean Clark]

100% testing error.

 

[tigresteve09]

A 100 ppm drop would correspond to a 14 dKH drop so the calcium value change is due to test error.

In a reef tank, for each 2.8 dKH alkalinity consumed, 18-20 ppm calcium and 1-2 ppm magnesium are consumed. You can use these ratios in a variety of ways. I recommend basing everything off alkalinity because the tests are generally accurate and repeatable.

Magnesium test kits are so error prone that I don’t own a test kit anymore. I follow Randy’s Magnesium Method and just dose 1-2 ppm magnesium for every 20 ppm calcium I dose. Periodic ICP shows this keeps it on target.

Hope that helps.

Thank you. I’ll test again. I think I read that a drop in nitrates causes an increase in alkalinity. Is that correct and would account for the increase in Alk?

 

[rishma]

Thank you. I’ll test again. I think I read that a drop in nitrates causes an increase in alkalinity. Is that correct and would the increase in Alk?

Yes, if 50 ppm nitrate is consumed it will raise alkalinity by about 2.3dkH. So that could account for 0.2dkh of your increase using the nitrate values you posted.

 

[BryanM]

Yep, always test again when an unrealistic change happens. bad reagents, bad technique, etc.... When it seems to bad to be bad, test again!

 

[art310]

Looking for feedback on how these parameters interact, if this makes sense, is ok and what I should start doing to stabilize. My take has been running for about 2 months. I started with mature bio media so it cycled pretty quick. My tank is a 32G AIO.

I tested two days for the following results.

My most recent test is below. The alkalinity rose, and calcium dropped 100 ppm. I used a salifert test and thought it had to be wrong so followed up with a Hannah test and confirmed it’s correct.


I’ve been dosing magnesium almost daily trying to get it up to 1350-1400 but it’s not really rising. I also dose Brightwell code A&B but don’t do it often because I don’t understand exactly how it works.

What system is this, and is it expensive

 

[tigresteve09]

Looking for feedback on how these parameters interact, if this makes sense, is ok and what I should start doing to stabilize. My take has been running for about 2 months. I started with mature bio media so it cycled pretty quick. My tank is a 32G AIO.

I tested two days for the following results.

My most recent test is below. The alkalinity rose, and calcium dropped 100 ppm. I used a salifert test and thought it had to be wrong so followed up with a Hannah test and confirmed it’s correct.


I’ve been dosing magnesium almost daily trying to get it up to 1350-1400 but it’s not really rising. I also dose Brightwell code A&B but don’t do it often because I don’t understand exactly how it works.

What system is this, and is it expensive

Are you asking what app it is? It’s Pocket Marine. I think it was $4.

 

[tigresteve09]

Thank you. I’ll test again. I think I read that a drop in nitrates causes an increase in alkalinity. Is that correct and would the increase in Alk?

Yes, if 50 ppm nitrate is consumed it will raise alkalinity by about 2.3dkH. So that could account for 0.2dkh of your increase using the nitrate values you posted.

Tested again this morning. Got 390ppm for calcium. Tested twice.

 

[BryanM]

Tested again this morning. Got 390ppm for calcium. Tested twice.

same test kit? Reagents go bad, I'd probably take a sample to your lfs for verification, and/or get a salifert test kit (assuming thats different than what you're using now), and test with that as well.

It just doesn't seem possible when alk and mag numbers don't correlate to that massive drop.

 

[tigresteve09]

Tested again this morning. Got 390ppm for calcium. Tested twice.

same test kit? Reagents go bad, I'd probably take a sample to your lfs for verification, and/or get a salifert test kit (assuming thats different than what you're using now), and test with that as well.

It just doesn't seem possible when alk and mag numbers don't correlate to that massive drop.

It’s a newer reagent kit I bought less than a month ago. Yesterday my first test was with a salifert and I thought it was reading low so I retested with my Hannah. I got 360-370 on both salifert and Hannah tests yesterday.

I dosed 5ml of Brightwell A & B last night after testing. So that should have raised calcium a little for today but not 30 ppm. So there’s definitely some inconsistencies with my tests.

I’ve been using distilled water for my Hannah tests. I’m going to try using some RODI water in the Hannah and see if it makes a difference.

 

[Randy Holmes-Farley Verified Community Expert]

Calcium testing can be fairly variable. I don’t test it.

 

[rishma]

I also don’t test calcium due to test results being imprecise. I just base everything off alkalinity tests.

 

[BryanM]

I’ve been using distilled water for my Hannah tests. I’m going to try using some RODI water in the Hannah and see if it makes a difference.

Hanna states to use deionized water, and I found this out with wildly inaccurate tests using RODI.

The hanna test also only uses .1ml of salt water for the sample, which makes this test kit particularly finicky, sadly.

 

[rtparty]

Hanna Calcium checker? If so, don't trust the results. Get a Salifert kit instead