Mg falling

gcrance · Sep 20, 2015

so i read through the other post on here and didn't really find an answer for whats going on here.

i tested for MG two weeks ago and was around 1050ppm so i figured it was time to dose up and get my mg back in the 1300-1350 range. ran one of the reef calculators and was looking at dosing nearly a gallon of the b-ionic mag. couldn't lay hands on a gallon quick but i did get one of the 950ml bottles. hooked it up on my dosing pump and its run off most the bottle in a week. tested again to see where i was at and turned up right around 950ppm. i thought it may be the test kit. salifert mg exp 05/2018
so i tried another kit and got the same. one of the unclear things though is do i go by the fluid level in the syringe or the bottom of the plunger. with the air gap it could be the difference in 100ppm or so measure. but the kit says the air gap wont affect it. i dont see how but either way im lower than last week. so i got some tropic marin mg powder and the reef calc again says im gonna need a lot to get it up.
216.6 tsps to be exact which totals out to 1083 grams. only 450g in a bottle so around two bottles.

does this sound legit to anyone else? seems like a **** pile of mg powder or liquid to add to raise the mg such a small amount.

also has anyone else ttried to pre mix this stuff? if i need two bottles i should be able to dilute the whole bottle into a gallon of rodi and let it chug along for a week but seems like it would precipitate out

twilliard · Sep 20, 2015

What salt are you using?

Randy Holmes-Farley · Sep 20, 2015

Ignore the air gap in a syringe. The position of the end of the plunger is what determines the volume dispenses..

It takes a massive amount of magnesium to boost magnesium that much. It is also VERY soluble in RO/DI, so that 's not generally an issue.

But aside from low salinity, I can't really think how you'd ever be able to get it that low without going a long time dosing only calcium and alkalinity in a fast calcifying reef tank.

So, I worry very much it is just testing error. Even with multiple tests.

So I'd confirm it again before dosing that much.

Magnesium depletion is usually 1 ppm per day or less. Often much less. Not more than about 1/10th the calcium depletion rate. So to deplete magnesium by 200-300 ppm would take a long time.

I absolutely guarantee magnesium did not drop by more than 100 ppm in two weeks. That is testing error, certainly.

backpack · Sep 20, 2015

Are you doing massive corrections to water chemistry that are causing things to fall out with the ph shift?

gcrance · Sep 20, 2015

i use reef crystals, but keep in mind i dont do water changes very much. i have done maybe 4 15 gallon water changes since january this year and ph stays pretty stable unless i have an issue with my dosser which will through it outta whack a little. calcium has always been stable i dont have much of anything to suck it up out of the water. been in the low to mid 400's since i started the tank and have never doessed it. i do go thought about 50ml of bionic alk a day to maintain 8.9-9.4dkh it shifts a little bit thought the year.

gcrance · Sep 20, 2015

any recommendations on a good mg test kit. the saliferts have always had a decnt rep. the one i had been using i bout in december of last year and the new one today. both reading the same ish

Randy Holmes-Farley · Sep 20, 2015

If B-ionic is your calcium and alkalinity additive system, magnesium should not be depleted at all since it should have an adequate amount.

So I even more strongly suspect a problem in salinity or testing.

For NSW to have 1050 ppm magnesium, the sg would have to be 1.0216.