Low Magnesium

[pixie.hallows]

Hi there!

I’m new to reefing. have a 10 gallon Nano tank that’s around 4 months old. Everything in the tank seems happy, but I’m consistently getting low magnesium readings. (Using Red Sea magnesium test kit and a timer). I do 20% water changes about every week to week and a half. Two weeks ago I started dosing 2x weekly with 1/2 tsp of the attached supplement in 1/2 cup water. Magnesium is still hovering around 1040 ppm. Last night I measured, added the magnesium, and this morning tested again and it was still the same (1040). Not sure what to do?

Other parameters:

Alk 9.2
Calcium 410
Nitrate 2.4
pH 8.2
Phosphate .13
Salinity 1.023
Temp 79.1

Photos of the tank and supplement attached. The feather duster got mad because I turned on the white light for the picture. I have Coralife LEDs that usually are kept on blue.

Any help would be appreciated!

 

[archercorals]

With a tank this small. Whenever something is out of wack, just do a 100% water change with salt that has numbers you are looking for

 

[Randy Holmes-Farley]

I suspect the measurement is test error. Try the test on some new salt water.

 

[Garf]

Salinity is also 10% too low.

Edit - may be even more than that, depending on the accuracy of the chosen salinity testing method and calibration.

 

[AstroCoral]

I’m also suspecting a test kit error, especially if everything is looking good in the tank and all other parameters are within normal limits.

 

[jda]

Recalibrate your refractometer and get your salinity up to 35 ppt. Low mag and/or low calcium are a warning sign that salinity could be off - not always, but an easy check.

 

[pixie.hallows]

I took a water sample to my LFS and it measured 1200.
I’m not disclaiming user error but I’m pretty meticulous with all my testing. Should I get a different brand of test kit other than the Red Sea? Is it possible one of the components of the kit is bad?

 

[gbroadbridge]

Your salinity is low which means all the other parameters will also be low.
If you're using a refractometer or EC probe to measure salinity recalibrate and then adjust salinity up to 1.026 (35PSU).

You can check your Mg test with freshly mixed salt water (at 35PSU).

I don't have much faith in LFS measurements as most are using cheap API test kits.

 

[apb03]

Testing mag can be a bit of a pain and is largely unnecessary. I barely test for it at all. Water changes keeps me good even with 130gal.

 

[bushdoc]

There's barely anything in your tank which would consume magnesium in significant amounts.
Your magnesium is low, most probably because of lower salinity/ sg.
Raise those and your magnesium will go up.
Most if not all hobby grade magnesium test are very finicky. I would keep Red Sea kit. If you really want you can check it against reference solution.

 

[iko2thdk]

I've repeated magnesium tests with salifert and red sea. Both kits had my Mg at about 1040. My S.G. is 1.026 (Milwaukee, calibrated every time) and my Alk is 7.7 (Hanna). All my parameters have been stable for some time yet for some reason I rarely tested Mg.

It seems like LPS, especially Hammers and Duncans are not tolerant of low Mg.
I just made a fresh batch of IO Reef Crystals and at 1.026 it tested 1400 for Mg.
I have a RSR350 mixed reef and I will begin to dose ESV Mg to raise that value. It does not seem to be the fault of the salt mix and my SG is certainly high enough. The tank does not suffer from low pH varying from 8.1-8.3 during a 24 hr span.

Thoughts would be appreciated...

 

[Randy Holmes-Farley]

I've repeated magnesium tests with salifert and red sea. Both kits had my Mg at about 1040. My S.G. is 1.026 (Milwaukee, calibrated every time) and my Alk is 7.7 (Hanna). All my parameters have been stable for some time yet for some reason I rarely tested Mg.

It seems like LPS, especially Hammers and Duncans are not tolerant of low Mg.
I just made a fresh batch of IO Reef Crystals and at 1.026 it tested 1400 for Mg.
I have a RSR350 mixed reef and I will begin to dose ESV Mg to raise that value. It does not seem to be the fault of the salt mix and my SG is certainly high enough. The tank does not suffer from low pH varying from 8.1-8.3 during a 24 hr span.

Thoughts would be appreciated...

To consume 300 ppm of magnesium would require consumption of about 3,000 ppm or more of calcium. Unless you added that much over time without magnesium, then consumption is not the cause.

Might have been bad batches earlier, or testing errors for salinity or magnesium or both.

It's fine to boost magnesium by whatever is needed, but before doing that' I'd propose this experiment:

1. test the salinity of both the tank water and the new salt water at essentially the same time with the same calibration on the Milwaukee.

2. Assuming #1 does not show the tank salinity is lower than the new salt water, test both the tank water and new salt water one after the other with the same kits.

If it passes both tests, I'd add magnesium to 1300 ppm.

 

[iko2thdk]

To consume 300 ppm of magnesium would require consumption of about 3,000 ppm or more of calcium. Unless you added that much over time without magnesium, then consumption is not the cause.

Might have been bad batches earlier, or testing errors for salinity or magnesium or both.

It's fine to boost magnesium by whatever is needed, but before doing that' I'd propose this experiment:

1. test the salinity of both the tank water and the new salt water at essentially the same time with the same calibration on the Milwaukee.

2. Assuming #1 does not show the tank salinity is lower than the new salt water, test both the tank water and new salt water one after the other with the same kits.

If it passes both tests, I'd add magnesium to 1300 ppm.

Thanks Randy. I will repeat all my tests for both the tank and newly mixed salt water and report back.

 

[Randy Holmes-Farley]

Thanks Randy. I will repeat all my tests for both the tank and newly mixed salt water and report back.

Looking forward to it!

 

[iko2thdk]

As promised, an update. Both newly mixed reef crystals (IO) and my aquarium are at 1.025 (Milwaukee). New water had a Mg level of 1400. After adding 150ml of ESV Mg over the last two days, my aquarium water is now at 1200 (Red Sea).

Cannot really explain this disparity, water changes are regular, just switched to reef crystals from Tropic Marin Pro Reef.

Going to keep dosing ESV to 1300 and monitor.

Thanks

 

[Randy Holmes-Farley]

Sounds good.

Happy Reefing.