Magnesium dropping like a rock!

[KeMiKiLL]

Added some corals to my tank a few days ago and, while I know they consume magnesium and calcium (among other things) from the water, this seems extreme. Tests about two days after adding them to the tank showed calcium at 500 and magnesium at 1320. Today, calcium is 496 with magnesium at 1170.

I did do a ~90% water change yesterday but I believe that shouldn't have changed my magnesium by much. The bucket of Aquavitro Salinity that was used shows magnesium levels basically at what mine were already at when mixed to 1.025. I'm confused... Is there something I'm missing that could cause such a drastic change this fast?

This is a Biocube 32 gallon tank.

When investigating, I did notice something I didn't catch previously. There is a black sponge between the return pump chamber and filtration chamber that has been collecting some really nasty dirt. Some of that dirt is sitting under my refugium basket too. I'll be siphoning that out and rinsing out the sponge in a moment, but that wouldn't cause this, would it?

 

[RedReefer]

What test kit are you using?

 

[KeMiKiLL]

What test kit are you using?

Salifert. Ran the test three times very carefully with different clean vials each time to be sure.

 

[RedReefer]

How long has the tank been running?

 

[KeMiKiLL]

How long has the tank been running?

About two months or so. Started with Turbostart 900 and closely worked with a LFS with regular tests and guidance throughout the cycle. When the cycle was complete we added CUC and all are fine. Two clowns also fine.
All parameter tests are where I would expect them to be except for the Mg.

 

[RedReefer]

What’s your salt mix

 

[RedReefer]

Have you changed any dosing or water change schedule?

 

[KeMiKiLL]

Just found a very useful thread:

why does my magnesium drop?

hey guys this is my first post on here. i always watch the vivd aquariums videos on youtube and i enjoy everyone of them. but i have been having little problem with my water parameters. im currently doing the red sea coral growth program and following their recommended water parameters. and it...

www.reef2reef.com

I think I'm done with the Aquavitro Salinity. This is the second time I've gotten complications after a water change using this. The last water change showed very high ammonia. I tested everything and it turned out to be my mixed water somehow. Now this.

I'll stick to the Red Sea Coral Pro for now.

 

[KeMiKiLL]

Have you changed any dosing or water change schedule?

N dosing but I did do that huge water change right before the Mg tanked. I didn't think that would do it as the Aquavitro Salinity salt states over 1300 Mg when mixed to 1.025.
I don't trust that product anymore as of now.

Anyone want have a large bucket of possibly questionable salt? lol

 

[RedReefer]

Glad you found a possible culprit.

 

[KeMiKiLL]

Glad you found a possible culprit.

Thanks. I hope this sorts it out. Just tested my newly mixed batch of Red Sea Coral Pro and Mg is at 1340. Water change time...

 

[Rmckoy]

I tested my magnesium today for the first time in months - a year .
I use the same aqua vitro salt .
my mag is 1300

 

[RedReefer]

Just FYI I use Red Sea blue bucket. Red Sea is a very good clean salt

 

[Rmckoy]

Just FYI I use Red Sea blue bucket. Red Sea is a very good clean salt

I’ve been using this same salt for years .

 

[KeMiKiLL]

I tested my magnesium today for the first time in months - a year .
I use the same aqua vitro salt .
my mag is 1300

It's weird, I know. The salt clearly lists what the content should be when mixed yet the only change that happened was the water change. Also, on yhe previous water change by Ammonia spiked hard. I tested everything. When I tested the left over mixed water, ammonia was high, so I checked the RO used to mix it - nothing. Then I spoke to some other hobbyists and read some threads where others had similar experiences. This Mg bottoming out is just the last straw for me with that product. I don't know if I got a "bad bucket" but, regardless, these surprises haven't been fun.

 

[Keen4]

Just found a very useful thread:

why does my magnesium drop?

hey guys this is my first post on here. i always watch the vivd aquariums videos on youtube and i enjoy everyone of them. but i have been having little problem with my water parameters. im currently doing the red sea coral growth program and following their recommended water parameters. and it...

www.reef2reef.com

I think I'm done with the Aquavitro Salinity. This is the second time I've gotten complications after a water change using this. The last water change showed very high ammonia. I tested everything and it turned out to be my mixed water somehow. Now this.

I'll stick to the Red Sea Coral Pro for now.

It’s the best salt

 

[Ghost25]

I'm sure Randy is a smart guy but I think in this case he doesn't know what he's talking about. If you search you'll find multiple threads where people ask why their magnesium drops so much and he tells them it hasn't, it's just an error etc.

I can say from experience it does drop more than 1ppm/ day like he claims. Way more. I have a 20 gallon tank and I've added over 300g of magnesium chloride in the last 3 weeks with no water changes between. Keep in mind this is magnesium chloride hexahydrate so most of that weight is water but that corresponds to drops of 800ppm in 24 days.

To be clear I don't know where it's going, it seems highly unlikely it's being incorporated into coral. Probably it's precipitating somewhere as an insoluble compound but I don't know.