I'm stumped ...

[LJC6780]

So my tank is about 2.5 months old. BC29. 1 bluefin damsel. Zoas, mushrooms and one recovering sun coral (accidentally tried to kill ... has 1 tiny head and about half of a larger one) have been there for quite some time. I recently added a Duncan, hammer and trumpet. Several snails, 2 hermits (both been there a while) and 1 peppermint shrimp that was just added.

Originally my mg was down in 900s but since switching to Reef crystals it has started coming up. My problem is that I can't get it over about 1230. I'm dosing fluval sea magnesium daily and it's dropping still. My calc is reading 480 and alk is 10. Those haven't changed in several days but the mag keeps dropping.

Anyone have any thoughts as to why my magnesium is dropping so quickly despite dosing yet my alk and calc are holding steady?

Here is my mg record. The notes are dosed after the test.

And I even dosed more than I have been yesterday and it dropped even lower today. So I dosed more.

Should I be doing something different? Dosing something different? I wouldn't worry as much but I don't think my corals are as happy as they could be. My mushroom rock does look nice and full today though ... maybe the best it has looked!

My phosphates are finally getting down to a good level too. Down to 0.095 today. Aiming for the 0.03-0.05 range.

 

[bdare]

It normally takes a lot of Mg supplement to increase Magnesium.
What sg are you mixing your water change water to? How are you measuring salinity?

 

[LJC6780]

It normally takes a lot of Mg supplement to increase Magnesium.
What sg are you mixing your water change water to? How are you measuring salinity?

1.025 refractometer calibrated to RO water.

Tank holds steady at 1.025. I use an ATO to hold water level.

The reason I was just dosing 7.5ml is that is how much it says to dose for my tank size weekly. I figured daily dosing would raise it but it isn't. Increasing the dose doesn't seem to be helping either. Should I up it to like an ounce or something?

 

[bdare]

1.025 refractometer calibrated to RO water.

Tank holds steady at 1.025. I use an ATO to hold water level.

The reason I was just dosing 7.5ml is that is how much it says to dose for my tank size weekly. I figured daily dosing would raise it but it isn't.

I don't know how much of a difference it's making in this instance, but it is suggested to use calibration fluid instead of RO water. Just like when you calibrate a pH probe for salt water with 7 and 10 soltuions because your expected test result is around8, you would use salinity calibration fluid because it's closer to your expected value. It just helps reduce the variance if you will...

There are several dosing calculators online which will tell you how much of a given supplement is required to maintain the level you're looking for. I use the diy mg from brs. I don't know if they have your specific product listed. I would google reef dosing calculator and see if you can find one that includes the mg supplement you are using.

 

[LJC6780]

I don't know how much of a difference it's making in this instance, but it is suggested to use calibration fluid instead of RO water. Just like when you calibrate a pH probe for salt water with 7 and 10 soltuions because your expected test result is around8, you would use salinity calibration fluid because it's closer to your expected value. It just helps reduce the variance if you will...

There are several dosing calculators online which will tell you how much of a given supplement is required to maintain the level you're looking for. I use the diy mg from brs. I don't know if they have your specific product listed. I would google reef dosing calculator and see if you can find one that includes the mg supplement you are using.

Would the salinity being off by a point or two make the magnesium deplete as fast as I can put it in? There isn't even THAT much coral in the tank. And my calc and alk aren't changing.

I'll look up the thing on BRS.

 

[wkscott]

BRS calculator

http://www.bulkreefsupply.com/reef-calculator

 

[Randy Holmes-Farley Verified Community Expert]

The magnesium is not being depleted by consumption in the tank. It can slowly drop if water used for water changes is lower than your tank. Natural seawater at a sg of 1.0264 (35 ppt) has about 1280 mg/L magnesium. At 1.025 it will only have 1212 mg/L, so being off will appear to cause lower magnesium.

Aside from that, the only possible explanation for rapidly dropping magnesium is test error, which is VERY common.

Most of your magnesium changes are test error. It doesn't jump up and down on its own by 50 ppm in a day or two (up can be true with a lot of dosing).

 

[LJC6780]

The magnesium is not being depleted by consumption in the tank. It can slowly drop if water used for water changes is lower than your tank. Natural seawater at a sg of 1.0264 (35 ppt) has about 1280 mg/L magnesium. At 1.025 it will only have 1212 mg/L, so being off will appear to cause lower magnesium.

Aside from that, the only possible explanation for rapidly dropping magnesium is test error, which is VERY common.

Most of your magnesium changes are test error. It doesn't jump up and down on its own by 50 ppm in a day or two (up can be true with a lot of dosing).

I haven't done a water change since Saturday evening. I'm meticulous about being consistent and following directions for testing. I'm using a Salifert magnesium test. My tank is a steady 1.025, going out and going in so it should at least stay steady. I've dosed magnesium daily and it continues to drop, and it's not going out with a water change. My calc and alk are holding steady and not fluctuating ... I thought they were supposed to work together and be used up together.

 

[Randy Holmes-Farley Verified Community Expert]

Testing error. No other possibility.

 

[bdare]

Testing error. No other possibility.

Agreed. Mg just simply doesn't drop like that.

 

[Randy Holmes-Farley Verified Community Expert]

I guess one other possibility is changes in salinity between measurements, making everything rise and fall together.

 

[ws6kid]

What brand of test are you using? Some of them are terrible.

 

[jrr98002]

One possibility I was thinking of that would lead to decreasing Mg levels would be some sort of precipitation going on. It's been a VERY long time since I've done a lot of nitty-gritty analytical/inorganic chemistry (my field is theoretical computational physical chemistry), but I don't believe this is what is happening, as I can't recall of anything that would be in your water that might be precipitating out the Mg to that degree. I think magnesium carbonate is insoluble if I recall, but you said your alk is steady. Any thoughts of anything that could make this be the culprit, Randy? I'm also leaning towards testing error IME, or perhaps you may want to consider getting a brand new kit, as sometimes even with proper analytical techniques, failing reagents will screw you no matter how hard you try.

 

[jsker]

What brand of test are you using? Some of them are terrible.

+1

 

[jsker]

One possibility I was thinking of that would lead to decreasing Mg levels would be some sort of precipitation going on. It's been a VERY long time since I've done a lot of nitty-gritty analytical/inorganic chemistry (my field is theoretical computational physical chemistry), but I don't believe this is what is happening, as I can't recall of anything that would be in your water that might be precipitating out the Mg to that degree. I think magnesium carbonate is insoluble if I recall, but you said your alk is steady. Any thoughts of anything that could make this be the culprit, Randy? I'm also leaning towards testing error IME, or perhaps you may want to consider getting a brand new kit, as sometimes even with proper analytical techniques, failing reagents will screw you no matter how hard you try.

Could be from the high alk the the magnesium in precipitating. I know when add Mg and to add it at the same time as alk for the reason it will precipitate the Mg. Not a chemist so in my terms. alk will void the Mg if added together.

 

[reeferfoxx]

I'm using a Salifert magnesium test.

 

[jrr98002]

Salifert is the brand I've used for years as well, and always proved to be quite reliable. Also, I'm not necessarily buying my previous post about precipitation of Mg given the fact that Ca++ and Mg++ behave nearly chemically identically (given that both are Group 2 elements and only separated by that one extra electron shell), so I'd also have suspected some calcium decrease if precipitation were indeed happening, along with the alk. Of course, I'm secretly waiting on Randy to respond with some unique fact of chemistry I don't know.

 

[LJC6780]

Testing error. No other possibility.

Testing error EVERY time? I get out the directions and follow to the letter. I don't know how else I could be more precise unless the test is just crap.

 

[LJC6780]

I guess one other possibility is changes in salinity between measurements, making everything rise and fall together.

My salinity has held steady at 1.025. Calcium has been 480 until today which somehow was 500. It did that the other day too and I even tested twice to be sure. Alk holding steady at 10. I use clean vials and measure out 5ml with a syringe so each test is the same. I make sure every drop lands in the vial. I count very carefully. I can read and follow directions.

 

[LJC6780]

Could be from the high alk the the magnesium in precipitating. I know when add Mg and to add it at the same time as alk for the reason it will precipitate the Mg. Not a chemist so in my terms. alk will void the Mg if added together.

I'm not adding anything for alk.