Just say NO to magnesium testing: RMM is born

[Tahiti]

I use All for Reef and only test for Alk. So sounds good to me!

 

[deadboi77]

And just when I was about to order a new mag test I stumble across this thread..

 

[vahegan]

Hanna test is very bad, results all over the place. I’ll just keep dosing with the brs calcium, alk, and mag along with the shine andd should get a good feel for how much the tank consumes.

Are you using their updated kit with new firmware (the one that has the 3-min timer built in)? I was seeing crazy results with the initial version, which was faulty, but they shipped me the new version free, and I am seeing very stable results ever since (and the response to my adjustments in the amount of magnesium supplement also matches the expectation).

 

[taricha]

my mag seems to drop fast on me i dont know why i dont even have that many corals

One of Randy's points in this thread is that test error is highly likely to be larger than any actual change in Mg concentration over some reasonable trending time period.
So look at salinity like @Garf said, but other than that - it just isn't moving that much.

 

[Key Largo]

How about if we are using Kalk?

 

[ctopherl]

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.

Step 3 feels easier said than done. I have my separate calcium and magnesium 2 part solutions. How do I know what 5-10% is? Test the 2 part solutions directly? Mix them with some arbitrary amount of RO water to dilute a bit and then test?

 

[Randy Holmes-Farley]

my mag seems to drop fast on me i dont know why i dont even have that many corals

IMO, that would be test error or a steady salinity drop. There’s just no mechanism for magnesium to drop anywhere near as fast as calcium.

 

[Randy Holmes-Farley]

How about if we are using Kalk?

Then you might regularly dose magnesium or boost your water change water i0f you want to maintain the salt mix level. I did the latter. Thus from one of my articles.

Magnesium (Mg). Although I do not add magnesium to the aquarium, I have been adding it to the salt mix. In the past, Instant Ocean was on the low side in magnesium, and I determined that adding about 150 ppm (mg/L) of magnesium to it would get the aquarium water about where I wanted it. However, several years ago, the makers of IO boosted the magnesium in it. I didn’t bother to decrease the additions I was making to the new salt mix. It appears I should have stopped, as the magnesium in the tank was higher than I prefer (1500 mg/L). If I stop these additions, it will likely drop significantly, probably by about 150 ppm to 1350 ppm, and that’s a fine target for my aquarium. So, my main action item from this set of results is to stop adding extra magnesium to the salt (obviously, ordinary magnesium testing with a kit could also have determined this result).

 

[Randy Holmes-Farley]

Step 3 feels easier said than done. I have my separate calcium and magnesium 2 part solutions. How do I know what 5-10% is? Test the 2 part solutions directly? Mix them with some arbitrary amount of RO water to dilute a bit and then test?

What two part? My two part is properly designed for dealing with magnesium. BRS uses my recipe. Just add the third part as intended, which was never supposed to be by measurement.

 

[Paullawr]

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.

Dosed it previously. Accidentally overdosed it once (maybe twice). It's a pain to get out of the system when you OD. Don't dose at all now. Just use salt mix, or natural filtered sea water.

 

[sawdonkey]

What would you consider a good range for magnesium?

I go with a big squirt when I think to do it. My methods are pretty precise. In my many years of testing mag, I never got a result that was far from good. So about a 7-8 years ago, I just stopped testing and give the tank a shot every now and then.

 

[ctopherl]

What two part? My two part is properly designed for dealing with magnesium. BRS uses my recipe. Just add the third part as intended, which was never supposed to be by measurement.

I use the BRS pharma 2 part. Is it safe to assume that 10% of solution gives you 10% ppm value? Meaning for every 10mL of CA solution dose 1mL of MG solution?

 

[Randy Holmes-Farley]

I use the BRS pharma 2 part. Is it safe to assume that 10% of solution gives you 10% ppm value? Meaning for every 10mL of CA solution dose 1mL of MG solution?

That is my recipe, which is designed for FIXED part 3 dosing, not measurement based dosing of magnesium.

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

You dose 1 mL of the third part for each 6.2 mL of the calcium part.

 

[ctopherl]

That is my recipe, which is designed for FIXED part 3 dosing, not measurement based dosing of magnesium.

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

You dose 1 mL of the third part for each 6.2 mL of the calcium part.

There we go! I wasn’t confident in my ability to figure out that 6.2:1 ratio so that is helpful. I will try it and see where my Mg ends up thank you!

 

[Kfactor]

what if your using a calcium reactor ? do i need to add more mg to it ?

 

[Randy Holmes-Farley]

what if your using a calcium reactor ? do i need to add more mg to it ?

What are you using for media? Do you do water changes? Have you tested magnesium?

 

[ReeferSamster]

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

Yep. For the 1st few years I didn't even test for magnesium. Only alk and calc. Then I started really nerding out on reefing and started chasing numbers with all these test kits. Barf. And then I just got busy and stopped testing, but maintained water changes and alk calc and mag and occasional balling c part when I remember, by eyeballing it every day or every other day.

I think the last time I even measured mag...or even alk and calc, was a few years ago. I've had this reef world so long I can eyeball it and get a spidey sense if I notice abnormal behaviour from flora or fauna in the reeftank.

 

[adammarcos]

I like this method. I hate testing magnesium.

Nox Vidmate VLC​

 

[diver22]

OK, have a question, was looking to make my own mix would this Mag work to mix with Epson salt ? any recommendation for Epson salt or anyone will do ?



Or what would people recommend besides buy from BRS ... lol

Thank You !

 

[Randy Holmes-Farley]

Yes, that material is likely a good choice. The only concern is the possibility of ammonia. If you use small amounts it will be fine, but for a big boost, I’d measure the ammonia effect in a small test batch of tank water with some added.