Magnesium testing

FishingLovingSons

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Hi fam! Getting some frags (LPS and softies) shipped to me next week; fine tuning tank for their arrival. I haven’t ever test for Magnesium in this tank before but could not get a reading today! Below is current parameters:

20g Long- running January. Hob Tidal 55 and AC20 modded for fuge- sea lettuce. No sump.

Stock- Royal Gamma, Pink Spot Goby, 6 line, pistol shrimp, tons of snails and a few hermits

1.025-1.026 specific gravity (looks like 1.0255)
79.8 degrees
pH 8.0-8.2
dKH 8.75ish
NO3 5-10
NH3/NH4 0
NO2 0
(Red Sea Marine Care test kit)

I ran Mg test (Salifert) 3 different times and every time I used all the reagent without any color change. According to chart maximum is 1500 but I didn’t get blue or gray at all. Test kit says good through 12/21 so definitely not close to expiration.

What should I do to get an accurate reading? Does this even make sense? Which test kit do you use for Mg?

Any insight/help is much appreciated. Please and thank you!

image.jpg


FYI- rescaped recently and added top bridge rock and front sandbed rock dry... that’s why they’re so bright. All other rocks were dry but in tank since January; CUC since March/April.
 

WIReefer

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I use Red Sea/trident for my mag test. Looks like you don’t have much in there your weekly water changes should be fine for keeping your mag level in range. What salt are you using? It would be good to invest in a good PO4 test kit as well I suggest the Hanna ulr. Nice looking tank! Congrats on the new coral shipment!
 

nereefpat

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I ran Mg test (Salifert) 3 different times and every time I used all the reagent without any color change. According to chart maximum is 1500 but I didn’t get blue or gray at all.

Try filling the syringe again. Add the volumes of reagent together. It's something like 30 ppm for every 0.02 mLs on the syringe.

Salifert is the standard Mg kit. It used to be the only one, now there are others.

Are you adding anything to the tank (supplements) that might increase Mg?
 

PatW

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It is easy to get a really high reading on a Mg test. But 1500 is pretty high. It is higher than any salt mix I know of. Mg should not spontaneously concentrate in the tank so I would regard that result as doubtful.

The problem is that (IMO) Mg tests are a bit wacky. I use salifert and aqua forest. My Salifert results fit closely with the published value of my salt mix but aqua forest is almost 1500 (and it is the top rated Mg test by Bulk Reef Supply. So go figure.

Even a tank chock full of fast growing SPS corals probably can be have its Mg maintained by water changes.

ALK and Calcium are the stuff they really consume and that require dosing.

So I would say, don’t sweat it. Water changes should keep it in line. If you have a trusted LFS, you might ask them to test the water. If they use Salifert and get a different result, have them watch you test a sample and critique your method.
 
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FishingLovingSons

FishingLovingSons

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I use Red Sea/trident for my mag test. Looks like you don’t have much in there your weekly water changes should be fine for keeping your mag level in range. What salt are you using? It would be good to invest in a good PO4 test kit as well I suggest the Hanna ulr. Nice looking tank! Congrats on the new coral shipment!

I started with regular IO but switched to Reef Crystals a month ago... I should say started using Crystals in water changes since then. I’ve considered Hanna testers just expensive! Might be time to bite the bullet. Thank you; hope I can get the new corals to prosper!


Try filling the syringe again. Add the volumes of reagent together. It's something like 30 ppm for every 0.02 mLs on the syringe.

Salifert is the standard Mg kit. It used to be the only one, now there are others.

Are you adding anything to the tank (supplements) that might increase Mg?

I’ll try again refilling syringe. I figured there was no way I was above 1500 Mg so dumped it all and tried again. Only additives have been some Continuum products: Bacter Gen-MD and Coralline Purple-CX. Trying to improve my coralline growth and the fish were just introduced on Wednesday. That’s why I used the Bacter Gen-MD. I’ll check both of these again but didn’t see anything about increased Mg.

It is easy to get a really high reading on a Mg test. But 1500 is pretty high. It is higher than any salt mix I know of. Mg should not spontaneously concentrate in the tank so I would regard that result as doubtful.

The problem is that (IMO) Mg tests are a bit wacky. I use salifert and aqua forest. My Salifert results fit closely with the published value of my salt mix but aqua forest is almost 1500 (and it is the top rated Mg test by Bulk Reef Supply. So go figure.

Even a tank chock full of fast growing SPS corals probably can be have its Mg maintained by water changes.

ALK and Calcium are the stuff they really consume and that require dosing.

So I would say, don’t sweat it. Water changes should keep it in line. If you have a trusted LFS, you might ask them to test the water. If they use Salifert and get a different result, have them watch you test a sample and critique your method.

Thank you! Don’t know the LFS that well but one not too far away; I’ll stop by this weekend and let them test for me.
 
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FishingLovingSons

FishingLovingSons

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I mixed a 5G bucket up to 1.026 yesterday; lid on with heater and powerhead running in it. I’ll change 2.5 gallons ach this weekend and then how long should I wait to do another WC after coral frags are introduced? Is there a standard “wait 24 hours” or anything?

I appreciate all of your help!!!
 
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FishingLovingSons

FishingLovingSons

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Just tested again after 3 gallon WC (did the WC about 2 hours ago.) Had to refill syringe with reagent and it finally worked with about 0.85ml left. According to @nereefpat that would be 1500 (full syringe) + 225 (30ppm every .02ml).

1725 Mg after 15% WC! Guessing I should just keep doing 10%ish WC until numbers come down?
 
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FishingLovingSons

FishingLovingSons

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I’ll just take samples to my lfs; getting ridiculous readings in freshly mixed SW too. Took full syringe plus an extra .15-.2ml. Reef Crystals and RODI at 1.026sg... I must be doing something wrong. Followed step-by-step instructions every time... at a loss now. Chalk it up as user error until independent test shows me otherwise.

Thank you all for the help/insight!
 

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im in the same boat sorta. I have a old salifert test kit, (not expired yet, exp date is feb 2021), and a newer Redsea Pro kit. yesterday i performed tests with both for to crosscheck numbers, redsea initially read 1380, and my salifert 980. today i went to the LFS and they checked with their salifert kit, they got a 1290 reading.

at first i was thinking redsea was too high, but now im thinking my salifert is just old or something.. even though not expired. even after a dose of skeletal elements and mg doser increase, no changes in mg today (side note, odd it didnt change at all).

im sticking with redsea numbers and aiming for top of the Mg range for reefs when testing with them (1400)~ , cause they seem a bit higher anyway.
 

Randy Holmes-Farley

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im in the same boat sorta. I have a old salifert test kit, (not expired yet, exp date is feb 2021), and a newer Redsea Pro kit. yesterday i performed tests with both for to crosscheck numbers, redsea initially read 1380, and my salifert 980. today i went to the LFS and they checked with their salifert kit, they got a 1290 reading.

at first i was thinking redsea was too high, but now im thinking my salifert is just old or something.. even though not expired. even after a dose of skeletal elements and mg doser increase, no changes in mg today (side note, odd it didnt change at all).

im sticking with redsea numbers and aiming for top of the Mg range for reefs when testing with them (1400)~ , cause they seem a bit higher anyway.

Are you certain you are not reading the salifert syringe backward? Many folks do that.
 

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