Mg add How many Days? You kiddin' me?

dbowman5 · Apr 17, 2020

I just started testing Ca and Mg. both were low so i did 10% WC. and ordered E.S.V. B-IONIC 2-PART CALCIUM BUFFER and Brightwell Aquatics Magnesion
the Magnesion came today. the reading was 975 so i calculated about 1500 ml for 100 gal system. the max daily dose according to their instructions is 10 ml per 20 gal. or 50 ml per day.. 30 days to get it to 1365 if none is consumed during the month? are they serious?

Rybren · Apr 17, 2020

What test kit are you using and did you repeat the test? I suspect testing error. Can you try a different test kit?
What salt mix are you using?

dbowman5 · Apr 17, 2020

Salifert Mg test Did not repeat but will now. that is the only Mg test I have
the readings on the 11th were:
Ca is 321 I checked it with the Hanna Marine Calcium checker
my Mg is 975 checked with Salifert test
alk is 6dKh API
pH 8.1 API
Nitrates 0 with API tests
sp. Gr. 1.025 Refractometer
temp 81 deg.
Instant Ocean which is:
Ca 400
Mg 1350
dKh 11

I will test freshly made SW
fresh 1.025 sp. gr tests = 1000 ppm Mg
today, the 17th, after adding 150 mls of Magnesion which should have raised the tank concentration 39 ppm the tank is reading 990 i will test again tomorrow, thank you.

Randy Holmes-Farley · Apr 17, 2020

The magnesium sounds like an error. It would take a very long time adding lots of calcium and alk and no magnesium to get to that low of a level.

dbowman5 · Apr 17, 2020

as above the test seems to be checking low on new water. unless my refact is off. I haven't added any dosing chemicals till today adding Mg. but i haven't done many water changes either.

Rybren · Apr 18, 2020

If the calibration is off on your refrac, then that could explain your results. Get some calibration fluid and recalibrate it.
The API alk test isn't the greatest. It will get you in the general ballpark, but due to the large drop size, it could easily be off by 1-2 dKH.

dbowman5 · Apr 18, 2020

Rybren said:
If the calibration is off on your refrac, then that could explain your results. Get some calibration fluid and recalibrate it.
The API alk test isn't the greatest. It will get you in the general ballpark, but due to the large drop size, it could easily be off by 1-2 dKH.

thanks, everyone in the tank is happy, what's not to love?

dbowman5 · Apr 18, 2020

I checked my refract' on reefkeeping homemade calibration solution and it is close. I am thinking that the salinity number is close. if the salifert and Hanna numbers are off on new water maybe i could make a controlled solution. test it. make a volumetric addition of the Magnesion and retest.

Randy Holmes-Farley · Apr 18, 2020

dbowman5 said:
I checked my refract' on reefkeeping homemade calibration solution and it is close. I am thinking that the salinity number is close. if the salifert and Hanna numbers are off on new water maybe i could make a controlled solution. test it. make a volumetric addition of the Magnesion and retest.

Which Hanna and Salifert numbers (what parameter? what value?)?

dbowman5 · Apr 18, 2020

Randy Holmes-Farley said:
Which Hanna and Salifert numbers (what parameter? what value?)?

the readings above,Salifert Mg: new 1.025 sp. gr. SW 1000 ppm Mg tank Water 990 Mg tank water before Magnesion add of 39 ppm 975 ppm
Hanna Ca: tank water 321 Ca
Thanks Randy!

has anyone noticed any errors in the test instructions that might be factors in errors? Perhaps mis-understandings or ambiguities in language?

Randy Holmes-Farley · Apr 18, 2020

Might you be reading the syringe backward? Some people do. If you use a full syringe to get to the endpoint, it is a high magnesium reading, not a low one.

Rybren · Apr 18, 2020

Randy Holmes-Farley said:
Might you be reading the syringe backward? Some people do. If you use a full syringe to get to the endpoint, it is a high magnesium reading, not a low one.

With the Salifert Mg test, the end of the black tip of the plunger should be at the 0.34ml mark to have a reading of 990ppm. Are you using the plastic tip on the syringe and is there some air in the syringe when you draw in the plunger to the 1ml mark? The answer should be yes to both.

mache62 · Apr 18, 2020

If your Ca is 340 then I'm guessing your Mg is probably right. I've always understood the Mg to be roughly 3x Ca number. Personally I would start with Alk and bring that up to 7-8 then bring up Ca to 400. Then see what the Mg is doing. Once they are all in alignment you should be good then maintain a steady Alk and Ca.

Potatohead · Apr 18, 2020

Everything you are testing is low. I would highly suspect the salinity is also low and causing the previous condition.

dbowman5 · Apr 18, 2020

Randy Holmes-Farley said:
Might you be reading the syringe backward? Some people do. If you use a full syringe to get to the endpoint, it is a high magnesium reading, not a low one.

thanks yes holding the syringe tip up

dbowman5 · Apr 18, 2020

Rybren said:
With the Salifert Mg test, the end of the black tip of the plunger should be at the 0.34ml mark to have a reading of 990ppm. Are you using the plastic tip on the syringe and is there some air in the syringe when you draw in the plunger to the 1ml mark? The answer should be yes to both.

yes and yes

dbowman5 · Apr 18, 2020

mache62 said:
If your Ca is 340 then I'm guessing your Mg is probably right. I've always understood the Mg to be roughly 3x Ca number. Personally I would start with Alk and bring that up to 7-8 then bring up Ca to 400. Then see what the Mg is doing. Once they are all in alignment you should be good then maintain a steady Alk and Ca.

i get the 2 part Monday i was under the impression that if the Mg is low the Ca precipitates I will work on the three in the order you suggest

dbowman5 · Apr 18, 2020

Potatohead said:
Everything you are testing is low. I would highly suspect the salinity is also low and causing the previous condition.

understood. the RODI is reading 0.001 the tank water reads 1.025. The IO salt is in bags and i have used salt from 2 bags. the odds of both bags being off? hard to say.

Potatohead · Apr 19, 2020

dbowman5 said:
understood. the RODI is reading 0.001 the tank water reads 1.025. The IO salt is in bags and i have used salt from 2 bags. the odds of both bags being off? hard to say.

I would highly recommend getting some refractometer calibration solution. I would be very surprised if you are not mixing this salt in the 1.021 - 1.022 range unintentionally.