Need to raise magnesium

Sea-air-a · Nov 12, 2017

Mag has went from 1,050 to 1,000 in one day
I started dosing Kent’s mag and it says 1 ml a gallon?
It went back up to 1,050 two days ago the day after I started dosing....
I got home last night from work and noticed my magnificent anemone was the smallest I had ever seen it! so I freaked out and tested my tank, sure enough my mag is now at 950! Everyone else is good, calcium is a tiny but high but that is it
I added 25 ml to my tank and I’m going to test again today.

I have the LED 32G Biocube by Coralife,
The biocube protein skimmer
About 35 pounds of live rock and about 35 pounds of live sand.
I have gotten all my water fresh and salt from the same LFS since the beginning. They told me a few weeks ago my tank was looking awesome and was probably almost done cycling.
My tank is going on 3 months old.
They always told me 1,050 was fine because my tank is new vvv
I get it tested every 3 days at LFS and my tank is always fine.
I have a sandsifting star
2 polyp frags.
Retteri anemone
Carpet anemone smaller than a silver dollar
Dying trumpet I got for free at LFS
2 snails
A small blue hermit
Nigra Nudibranch
Tiger tail cucumber
Sea hair.
I had 2 two band Redsea clowns but changed them into 13.5 hospital tank because they have velvet and ich‍

My luck from the beginning hasn’t been the best, I’m just happy nothing has died since starting my tank.

Question is with info given what would be your suggested amount to be dosing my tank every night?
Is there a better product I can buy that will help raise it faster?

Randy Holmes-Farley · Nov 12, 2017

Sea-air-a said:
Mag has went from 1,050 to 1,000 in one day

No, it did not.

Your test result may have, but it is in error, unless you changed it with a massive water change using a low magnesium mix.

Don't dose anything yet.

Randy Holmes-Farley · Nov 12, 2017

If alkalinity is not declining, then magnesium and calcium are not either.

What salt mix are you using and what salinity?

Are you dosing anything else, such as for alkalinity?

Sea-air-a · Nov 12, 2017

2 days before I did do a water change(5 gallons) so my calcium would drop from 500 my ALK at time was 10.
Nest day It dropped to 475 and ALK to 9 and that’s when I noticed my mag dropping.
I haven’t put anything else in my tank before, just the Kent mag.
I haven’t tested for ALK or calcium in 2 days just my magnesium last night because it was late.
I will do a full test on everything today again and see how my ALK and calcium are.
I am using Hanna checkers and double checking with api tests every time I do them to make sure I am not messing up.
Elos is what I am using for my magnesium tests.
I was showed multiple times by my LFS because I work there also just not in the fish department.

Sea-air-a · Nov 12, 2017

And about the salt mix they are using I’m not sure! Probably not smart of me but I have never thought to ask that.

Randy Holmes-Farley · Nov 12, 2017

If magnesium was really being consumed, in order to have lost 50 ppm of magnesium, you would have had to have lost about 93 dKH of alkalinity and 600 ppm of calcium since they are used together. Obviously that didn't happen overnight.

FWIW, magnesium testing problems are VERY common.

pdisner · Nov 12, 2017

Randy Holmes-Farley said:
If magnesium was really being consumed, in order to have lost 50 ppm of magnesium, you would have had to have lost about 93 dKH of alkalinity and 600 ppm of calcium since they are used together. Obviously that didn't happen overnight.

FWIW, magnesium testing problems are VERY common.

Wow! Really that much dKh? 93?!

Randy Holmes-Farley · Nov 12, 2017

pdisner said:
Wow! Really that much dKh? 93?!

Yes. Magnesium is really only consumed by incorporation into precipitating calcium carbonate. In such a structure (including coral skeletons, coralline algae, and abiotic precipitation on pumps and such) the amount of magnesium is pretty low.

A typical maximum incorporation rate for magnesium is 1.5 ppm magnesium for each 2.8 dKH of alkalinity and 17.5 ppm calcium. Many organisms that deposit aragonite skeletons actually incorporate a lot less magnesium.

Consequently, some people see very little magnesium depletion, but those who do do not usually see more than 1-2 ppm magnesium drop per day, and that's when dosing a lot of calcium and alkalinity, and no magnesium. You need to let that run many days to ever detect it with a kit.