Just say NO to magnesium testing: RMM is born

[Randy Holmes-Farley]

Do I ignore the magnesium testing? Each time I test using salifert, I am seeing over 1500 consistently

Yes, don’t test.

Have you used that kit on your new salt water, and what do you get?

 

[drblank1]

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing.

I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good methods need a catchy name.

Here it is.

1. NEVER measure magnesium. If it comes free from an ICP, sure, take a look. It's probably fine anyway. Don't buy or use a kit. Chances are the results are not very reliable, and most of the time, if there is a value out of the range of acceptable, it is more likely an error of some sort than a real result.

2. Use a decent salt mix at a decent salinity that has a starting level of magnesium and calcium that you like. If you cannot find one, it is easy to add a fixed amount of magnesium to a salt mix. I did that for many years, and rarely measured the tank itself.

3. ANY time that you add calcium, add 5-10% as much magnesium (so for 10 ppm calcium, add 0.5 - 1 ppm magnesium). If coralline is the main user of alk in your tank, use the 10%, if corals are, use 5%. A lot of products, like commercial two parts, AFR, CaCO3/CO2 reactors with suitable media, and my DIY two part systems all add magnesium for you, without measurement.

4. It will take a very long time for any sort of significant deviation to show, and if you also do water changes, it likely never will.

To some this will sound like a joke, but I think many reefers, especially newer reefers, would be better served by RMM than testing and retesting, dosing and redosing and then getting a new kit and testing again. Just a few minutes ago I finished a thread where a kit change gave a 200 ppm difference in magnesium.

Just say no. Exact magnesium levels are just not that important.

Randy, I 100% agree with you. I've been reefing for over 3 years now. Not once after testing, have I ever needed to dose Magnesium. I stopped testing for it about a year ago. Any one want to buy my Hanna mag testers.

 

[Reef Puncher]

i just bought a 2nd salifert test kit and a nyos test kit yesterday because i cant figure out what my mag is at. even today i still dont know.
1.) Salifert test kit 1 shows 1290
2.) Salifert test kit 2 shows 1250
3.) Red Sea Shows 1350
4.) Hannah shows 1800
5.) Nyos shows 1290

what the heck. what is my dang mag at. i even dose mag on an auto doser, quite a bit. im not sure if all my tests are off or if my tank is consuming mag....do corals or algae consume mag?

 

[Reefing_addiction]

I've always had higher Magnesium. My (home) test results ALWAYS shows above 1500, somewhere between 1500-1600.

I've had 2 ICP tests in the last year, one about a year ago at 1394 and one the end of this past August shows 1470. I contribute my higher Magnesium to the FritzPro salt that I use (states 1425 Magnesium mixed to 35ppm). I do not dose Magnesium.

I've wondered if higher Magnesium levels in my tank can lead to ill effects on the corals (I don't have that many right now) but wasn't sure if I should do anything about it or not.

I've also wondered why my tests at home with both a Red Sea Pro Magnesium test kit and a Salifert test kit both always showing above 1500.

think this post convinces me to just forget about testing Magnesium at home and just adjust if I need to after ICP tests.

My latest ICP test for magnesium was 1666…..

Everything in my tank is great

My LFS will test magnesium and it always registers above 1500

Me and the guy were talking and he said he has another long time reefer who comes in and will have him test magnesium- and if it’s below 1500 he doses….apparently higher magnesium keeps the algae away loo

 

[ReeferA]

@Randy Holmes-Farley "ANY time that you add calcium, add 5-10% as much magnesium (so for 10 ppm calcium, add 0.5 - 1 ppm magnesium)."
I dose kalk every night for 12 hours while maintaining a PH 8.3-8.35, should I dose Mg at the same time also?

 

[Randy Holmes-Farley]

@Randy Holmes-Farley "ANY time that you add calcium, add 5-10% as much magnesium (so for 10 ppm calcium, add 0.5 - 1 ppm magnesium)."
I dose kalk every night for 12 hours while maintaining a PH 8.3-8.35, should I dose Mg at the same time also?

I’d dose magnesium in that scenario, or use a higher mag mix for water changes. I simply boosted the salt mix I used for water changes, but adding it directly to the tank is also good. Timing doesn’t matter, and even once a week is fine.

 

[Liquidsnakes]

This is true. I use aquaforest reef salt. Everytime I do a water change 20% in my 50G and I did a MG test. The Mg was always the same, around 1410- 1420. Its a waste of time to do MG every week to the point i asked myself is this necessary. Now i only do Cal and Alk for testing. Sometimes nitrate and phos.

 

[GuppyHJD]

Yes, don’t test.

Have you used that kit on your new salt water, and what do you get?

I have not but now I am curious.

 

[GuppyHJD]

Yes, don’t test.

Have you used that kit on your new salt water, and what do you get?

Can my tank not be using magnesium?
I have not added any magnesium in 3 months. The tank is testing over 1500. ICP test in June was 1493. I am dosing BRS calc 2 part 60ml a day. I sent another ICP last week.

 

[ReeferZ1227]

Can my tank not be using magnesium?
I have not added any magnesium in 3 months. The tank is testing over 1500. ICP test in June was 1493. I am dosing BRS calc 2 part 60ml a day. I sent another ICP last week.

My guess - I would think you dosed it up high, stopped, and now your salinity is creeping up causing the higher reading or even more simply your test kit is just reading high/within margin of error and when this ICP comes back it should be at least less than 1493 with no additional magnesium added and the same salinity.

 

[Randy Holmes-Farley]

Can my tank not be using magnesium?
I have not added any magnesium in 3 months. The tank is testing over 1500. ICP test in June was 1493. I am dosing BRS calc 2 part 60ml a day. I sent another ICP last week.

What size tank?

 

[rtparty]

Can my tank not be using magnesium?
I have not added any magnesium in 3 months. The tank is testing over 1500. ICP test in June was 1493. I am dosing BRS calc 2 part 60ml a day. I sent another ICP last week.

I never dosed magnesium in over 2 years on this system:

Magnesium only came from water changes (I use salts with higher magnesium on purpose) and whatever Tropic Marin Part C has in it.

 

[Randy Holmes-Farley]

What size tank?

If we assume 100 gallons total volume, that 60 mL translates to about 6 ppm of calcium per day.

If all of the consumption was by coralline algae, magnesium consumption would be about 0.6 ppm per day. If it is by corals, it will be lower and maybe much lower.

So the max consumption here in 3 months with no additions is about 50 ppm, and
Easily could be half that.

Assuming you have done water changes during this time, I expect the magnesium consumption is just lost in the noise of testing.

That’s the reason for RMM.

That said, your levels are very high. Is there some reason you have them so high? Is it just from a salt mix?

 

[GuppyHJD]

If we assume 100 gallons total volume, that 60 mL translates to about 6 ppm of calcium per day.

If all of the consumption was by coralline algae, magnesium consumption would be about 0.6 ppm per day. If it is by corals, it will be lower and maybe much lower.

So the max consumption here in 3 months with no additions is about 50 ppm, and
Easily could be half that.

Assuming you have done water changes during this time, I expect the magnesium consumption is just lost in the noise of testing.

That’s the reason for RMM.

That said, your levels are very high. Is there some reason you have them so high? Is it just from a salt mix?

I have targeted Mag at 1450.
What size tank?

120gal

 

[Randy Holmes-Farley]

120gal

Then the expected magnesium drops will be even a bit smaller than calculated.

 

[GuppyHJD]

Then the expected magnesium drops will be even a bit smaller than calculated.

I got the ICP results today - 1453. So 3 months the Magnesium dropped 41 ppm.

 

[Randy Holmes-Farley]

I got the ICP results today - 1453. So 3 months the Magnesium dropped 41 ppm.

That’s reasonable.

 

[GARRIGA]

If magnesium is often held at three times calcium then wouldn’t it reduce by three times calcium consumption?

 

[TokenReefer]

Is it possible to reach a coral biomass that processes ammonia at a rate it outcompetes nitrifying bacteria to the point they are no longer present (or kept at very low levels)?

 

[Garf]

If magnesium is often held at three times calcium then wouldn’t it reduce by three times calcium consumption?

Nah, it's about 10% of calcium for some things, less for others.