Mg increases without dosing

[Herpdederp]

So I have not dosed any Mg in the last month and a half, all the products I use to maintain the tank does not contain Mg. Anyone experience something similar before? Kh is being consumed at around 0.5 every 4-5 days. Corals are medium load 95% softies 38 gallon.

APR	Mg
2
3	1350ppm
5
6
7
8	1440ppm
9
10	1410ppm
11
13
14
16
17	1410ppm
18
19
22
24	1410ppm
26
27
28	1360ppm
29
30	1420ppm
MAY	Mg
1
2
4	1370ppm
6
8
11	1440ppm

If there is any other relevant information that would help figure out what is wrong please don't hesitate to ask. Your input is much appreciated!

 

[EeyoreIsMySpiritAnimal]

How often are you doing water changes, and what's the Mg level of your saltwater?

 

[Herpdederp]

How often are you doing water changes, and what's the Mg level of your saltwater?

I stopped changing water from taking directly taking and replacing water in the tank 4 months ago, just top off with RODI around 8 gallons out of 48 gallons.

 

[Sean Clark]

What test are you using?

 

[Herpdederp]

salifert

What test are you using?

I thought could be a test kit error but I picked up another set and same results :/

 

[Herpdederp]

Corals aren't growing as fast as they should be too, no idea what could be causing the chemistry imbalance.

 

[Herpdederp]

I've also noticed some black soot on the micro algae in the fuge, not sure if that means anything. It's sticky but can be rinsed off easily.

 

[ZombieEngineer]

Due to the random and sporadic nature of your readings, I'm inclined to believe that testing error is the fault here. Mg consumption is usually pretty slow (approximately 2% of dKH but I can't remember it's by weight or ppm). Your spikes and drops just seem way too high to be actual changes. I would expect a small increase during water changes (ex my RC salt tends to mix at 1440 and if my tank was 1350 and I did a 10% water change I would expect 1359 immediately following). My tank consumes 0.7dKH worth of additive and my MG drops by approx 3ppm per day without dosing.

I would run a few side by side tests with another test kit and the one you have and test each one like 5 times. See if you actually get consistent readings with one so you can confirm or rule out user error in your testing.

Is your test kit expired?

 

[Herpdederp]

Due to the random and sporadic nature of your readings, I'm inclined to believe that testing error is the fault here. Mg consumption is usually pretty slow (approximately 2% of dKH but I can't remember it's by weight or ppm). Your spikes and drops just seem way too high to be actual changes. I would expect a small increase during water changes (ex my RC salt tends to mix at 1440 and if my tank was 1350 and I did a 10% water change I would expect 1359 immediately following). My tank consumes 0.7dKH worth of additive and my MG drops by approx 3ppm per day without dosing.

I would run a few side by side tests with another test kit and the one you have and test each one like 5 times. See if you actually get consistent readings with one so you can confirm or rule out user error in your testing.

Is your test kit expired?

One around 5months old and the other I just got last week. I've only done two in a row to see if there is a big difference in the result. Next time I test will do 5 times and see what the results say.

 

[Hydrored]

Check that your salinity is accurate…

 

[Herpdederp]

Check that your salinity is accurate…

solid 0.025 for the past three months, I don't change water so the salinity in the tank only changes if I take water out directly from the tank.

 

[EeyoreIsMySpiritAnimal]

solid 0.025 for the past three months, I don't change water so the salinity in the tank only changes if I take water out directly from the tank.

1.025, I hope!

 

[Herpdederp]

1.025, I hope!

yes typo haha or everything would be ded x.x

 

[Hydrored]

solid 0.025 for the past three months, I don't change water so the salinity in the tank only changes if I take water out directly from the tank.

What are you using to add calcium and alk? What do your calc trends look like compared to Mag?

 

[Randy Holmes-Farley]

salifert

I thought could be a test kit error but I picked up another set and same results :/

Doesn't demonstrate a rise, only greater confidence in the current reading.

That said, the rise you see is small and if not test error, is likely due to changes in salinity. The up and down and up and down proves it must be salinity or test error.

A change from sg = 1.025 to 1.026 (which is within the error of most devices reefers use to measure salinity) will boost magnesium in normal seawater from 1212 ppm to 1260 ppm.

FWIW, magnesium cannot rise on its own. Changes come when it is added, salinity changes, it is consumed, or due to test error.

 

[Herpdederp]

Doesn't demonstrate a rise, only greater confidence in the current reading.

That said, the rise you see is small and if not test error, is likely due to changes in salinity. The up and down and up and down proves it must be salinity or test error.

A change from sg = 1.025 to 1.026 (which is within the error of most devices reefers use to measure salinity) will boost magnesium in normal seawater from 1212 ppm to 1260 ppm.

FWIW, magnesium cannot rise on its own. Changes come when it is added, salinity changes, it is consumed, or due to test error

Last month and a half I have not added anything which has Mg, which is why I'm baffled. The salinity stays the same as I don't do water changes only top off.

 

[gbroadbridge]

So I have not dosed any Mg in the last month and a half, all the products I use to maintain the tank does not contain Mg. Anyone experience something similar before? Kh is being consumed at around 0.5 every 4-5 days. Corals are medium load 95% softies 38 gallon.

APR	Mg
2
3	1350ppm
5
6
7
8	1440ppm
9
10	1410ppm
11
13
14
16
17	1410ppm
18
19
22
24	1410ppm
26
27
28	1360ppm
29
30	1420ppm
MAY	Mg
1
2
4	1370ppm
6
8
11	1440ppm

If there is any other relevant information that would help figure out what is wrong please don't hesitate to ask. Your input is much appreciated!

It's a test error. Maybe inconsistency, or perhaps a test that has been open too long.
The use by date only applies until opened.

 

[Herpdederp]

What are you using to add calcium and alk? What do your calc trends look like compared to Mag?

APR	Mg	Ca
2
3	1350ppm
5		410
6
7
8	1440ppm
9
10	1410ppm	405
11
13
14		435
16
17	1410ppm	460
18
19
22
24	1410ppm	425
26
27
28	1360ppm	460
29
30	1420ppm	455
MAY	Mg	Ca
1
2
4	1370ppm	435
6
8
11	1440ppm

I haven't dosed any Ca either @@

 

[Stigigemla]

Normally You have a span of +- 30 ppm with Salifert Magnesium test.
Take a look at Your values.
The first two is 1350 and 1440 Lets say they both should have been 1395.
Then we have 1410 3 times followed by 1360 and 1420. I value these 2 as 1390.
The last 2 is 1370 and 1440. Name these as 1405. I think You have a stable value around 1400.

The problems with Salifert Ca and Mg tests is that they use very small volumes. That means that you have to be extremely careful with the 2ml volume test water. The 1 ml is easier because that syringe is longer so You get a better precision with it. And it is better to be real slow at the endpoint.

I recommend that You take 2 tests the next time. And if they are different take a third. When You are in +-30 for Magnesium it is OK but when You get extremely skilled +- 10 can be possible.

More about the volumes:
In the end of the 2 ml syringe You can make about 20 drops per ml so the 2 ml is about 40 drops.
Half a drop left or not left at thew end of the syringe means 1/80 of the test value. That is near 20 in the magnesium value. A drop left on the the sides of the long 1 ml tip can make 70 mg less value.
It is extremely import to take the sample and test fluid in exactly the same way every time if You want consistent values.

I find it very good that You save Your values. That will make it easier to handle Your reef.
It took some years before i began to log but now I will never quit it.

 

[Randy Holmes-Farley]

Last month and a half I have not added anything which has Mg, which is why I'm baffled. The salinity stays the same as I don't do water changes only top off.

How do you know salinity stays the same? I expect test error is likely, but salinity does not stay exactly the same unless the water level is exactly the same. How closely are you controlling the water level?