Mg increases without dosing

[Herpdederp]

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.

I use an auto mixer with a small magnet spinning at the bottom of the vile. I also redid the test today and come up once with 1360

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.

So strange though, since I don't do any water changes directly from the tank water the Mg value should be slowly depleting,

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?

The water level never changes, I have a 4L ATO on top of the tank and always refill it before it's completely empty. I also use a salinity refractometer to check every week always at 1.025.

 

[ZombieEngineer]

So strange though, since I don't do any water changes directly from the tank water the Mg value should be slowly depleting,

Mg depletes incredibly slowly. Mine is 2-3ppm per day and I dose a LOT of soda ash, which precipitates quite a bit due to the high pH. I would reasonably expect if you are dosing baking soda at 2/3 the dKH useage as mine, that you would see maybe 1ppm per day consumption. If you are precise enough with your test to be +-30ppm, it would take months to notice the consumption change.

I would also advise against the no water change method. I know a few reefers that tried it and things went okay for about 6 months and then coral growth slowed a lot. ICP testing revealed depletion of important trace elements and after a few water changes and ICP recommended dosing things started to bounce back and they gave up on the no water changes. I considered the approach on my Ultra Low Maintenance tank, but decided to do Auto Water Change instead after talking to these guys and it worked out great.

 

[Herpdederp]

Mg depletes incredibly slowly. Mine is 2-3ppm per day and I dose a LOT of soda ash, which precipitates quite a bit due to the high pH. I would reasonably expect if you are dosing baking soda at 2/3 the dKH useage as mine, that you would see maybe 1ppm per day consumption. If you are precise enough with your test to be +-30ppm, it would take months to notice the consumption change.

I would also advise against the no water change method. I know a few reefers that tried it and things went okay for about 6 months and then coral growth slowed a lot. ICP testing revealed depletion of important trace elements and after a few water changes and ICP recommended dosing things started to bounce back and they gave up on the no water changes. I considered the approach on my Ultra Low Maintenance tank, but decided to do Auto Water Change instead after talking to these guys and it worked out great.

I hit that point around 1 month or so ago, and I started to dose K and A trace elements from Tropic Marin and the corals look a lot better. If the minor trace elements are not replaced by water change will have to supplement in other ways. I started off with water changes but didn't notice much difference after stopping, of course until the trace elements were all used up and I stocked the tank with more coral over time.

Thanks for the input with the Mg depalletization, much appreciated!

 

[Randy Holmes-Farley]

I use an auto mixer with a small magnet spinning at the bottom of the vile. I also redid the test today and come up once with 1360

So strange though, since I don't do any water changes directly from the tank water the Mg value should be slowly depleting,

The water level never changes, I have a 4L ATO on top of the tank and always refill it before it's completely empty. I also use a salinity refractometer to check every week always at 1.025.

Still, most ato have a limit of how closely they control the water level. Do you know what that is?

 

[Herpdederp]

Still, most ato have a limit of how closely they control the water level. Do you know what that is?

The difference with the one I'm using will be 100ml max, which wouldn't change the salinity enough. The difference in water level should not be that great, unless the set up is faulty. When I first installed it, it didn't dispense water even if both of the tubes was completely out of the water, but after adjusting it, it dispenses water without any issue. I stuck some tape at the ideal water level and it never goes 1cm above or below the line.