Why is my Mg rising without water changes?

[BurtMacklin]

Does anyone have any knowledge as to whether or not Red Sea Trace Colors A/B/C/D affect magnesium? I don't see it listed on the insert that comes with any of them, but since stopping water changes and dosing these trace elements, BRS calcium chloride, and BRS Soda Ash over the last 4 months my magnesium has been consistently increasing and now sits at 1650ppm. Ca and alk keep getting consumed faster and faster for which I adjust my dosing pumps. The coral are coloring up nicely and growing faster.

I have a lot of inverts and do not want to threaten them with Mg over 1700. All other parameters have been stable.

@vetteguy53081 indicated that Part B of Red Sea Trace Colors is known to have too high a concentration of Sulfates and these cause Mg to rise. I stopped adding Part B entirely at the beginning of December, but it continues to increase. I was also adding Brightwell Amino Acids, but stopped adding that as well.

My Salinity has not changed from 1.025

I'm wondering if there's a reason my Mg would stay this high or if anything in these other (Part A, C, or D) trace element additives cause an increase in Mg. I've tried two different salifert test kits. Red Sea Reefer XXL 750 (200 gallon)

SG: 1.025
T: 78F
KH: 8.6
Ca: 420
Mg: 1650
Nitrates: 1-2
Ammonia: 0

@Randy Holmes-Farley

 

[blaxsun]

Are you dosing or supplementing anything else other than what you indicated? You can reduce your magnesium level with water changes, so that's an option.

 

[BurtMacklin]

Are you dosing or supplementing anything else other than what you indicated? You can reduce your magnesium level with water changes, so that's an option.

Of course I could do a water change. I'm trying to figure out the source of the Mg though.

I listed everything I'm dosing.

 

[Randy Holmes-Farley]

The magnesium movement is a combination of test error and likely also salinity changes. It does not move around like that. It never rises on its own and never declines more than 1-2 ppm per day and not more than about 1/10th of the calcium decline over the same time period.

 

[BurtMacklin]

My salinity hasn't changed. I even just calibrated and checked again now and it's still exactly 1.025.

I'm not suggesting it went up on its own. I'm suggesting there is magnesium in the red sea trace elements and wondering if you or anyone else has knowledge of Mg being in these solutions for red sea trace colors. Vetteguy thought it might be part B, but didn't seem to be 100% sure that was correct.

Maybe the last 2 tests differences were due to error and its actually around the same since discontinuing part B a month ago. If that's the case, I would expect it to have dropped since I recently have been aggressively increasing my calcium and alk dosing to compensate for the rapid coral growth.

I've confirmed the numbers on 2 test kits and the value was consistently increasing when using those trace element solutions, so it must be due to one of those components. Do you have a recommendation for ruling out testing error? Should I take a sample to my LFS?

 

[blaxsun]

Per @Randy Holmes-Farley, I would probably try a (non) Salifert test kit first - something easy to use (Aquaforest and Nyos are really good).

 

[Randy Holmes-Farley]

Have you tried your test in new salt water?

trace element supplements typically cannot boost magnesium appreciably, even if they contain some, because too little volume is added.

 

[BurtMacklin]

Per @Randy Holmes-Farley, I would probably try a (non) Salifert test kit first - something easy to use (Aquaforest and Nyos are really good).

@Randy Holmes-Farley

Another Salifert test is static at 1650ppm
A new Nyos Mg test is 1575ppm

I have not had time to make a new batch of saltwater to test against, but the SG of the aquarium is still 1.025

I'll make some new salt and compare them both against it, but given 2 different Salifert test kits and a Nyos all show it elevated, I suspect it to be real.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley

Another Salifert test is static at 1650ppm
A new Nyos Mg test is 1575ppm

I have not had time to make a new batch of saltwater to test against, but the SG of the aquarium is still 1.025

I'll make some new salt and compare them both against it, but given 2 different Salifert test kits and a Nyos all show it elevated, I suspect it to be real.

Unless you added it without knowing it, all of the magnesium in your tank came from the salt mixes you have used. I'd try one of those kits on some new salt water. It may have excessive magnesium, your salinity may be higher than you think, or the tests are off.