What factors deplete magnesium?

I mean other than natural depletion as the corals use it up, etc.

My tank is a couple of months old, with very little in it so far. Just one torch coral, and a leather.

My parameters have been fairly constant for the last few tests (done every other day):

Ph: 8.4, Ammon: 0, Nitrite: 0, Nitrate: 0, Phosphate: 0, Calcium: 480, dkH: 9, SG 1.025

I just recently did a mag test after tangster suggested it in a thread I posted about a green algae bloom I was having.

My mg tested at 1050 ppm.

I use Instant Ocean salt mix, and I've been doing weekly 10% water changes in my 100 gallon tank (30 gallon sump, 250 lbs of LR).

Initially I used tap water to set up my tank (on the advice of my LFS manager). I have switched to RODI water now though.

Could there have been something in the tap water that reacts with magnesium and causes it to deplete? What other factors may have led to low mg?

Cheers.

 

Instant Ocean isn't made for reef tanks....it's made for fish only tanks. Aquarium Systems salt brand for reef tanks is called Reef Crystals. It's Instant Ocean that they add more Calcium and Magnesium to.

 

Well, there's another reason not to deal with that LFS store again. When I set up my system there, he assured me that tap water was fine, and that Instant Ocean was perfectly fine for a reef tank. :-/

It didn't deplete, it just wasn't there to begin with!

Thanks for the advice, I'll switch to reef crystals for water changes and dose with mg in the meantime.

 

In some places, tapwater is fine.....not many places, but there are places where it's fine.

Instant Ocean is also fine as long as you know what it's for and adjust yourself for it's failings in a reef tank. It's probably the most used salt there is.

 

what a difference between the 2 big al's. mine started me out with reef crystals and an RO unit. i like mine better.

 

Yeah, it's not like cost was a factor for the salt mix either. I don't have any hard feelings against him, as he saved me a bunch of money in other ways and threw in some extras. I think that he's just the type to cut corners here and there.

And I was too new to know any better! At least I learned better before I lost any live stock.

 

you can use epsom salt to raise mag. I use it. theres a calculator on this website for how much to add.

with calcium at 450, u want a target mag level at 1350.

mag is 3x more than calcium in a perfect world.

 

i use instant ocean all the time... i dont seem to have any problems? can the magnesium be coming from some place else?

 

Instant Ocean is LOW in both Calcium and Magnesium. As a result, they are low in these elements and will need to supplement them for LPS and SPS (and some softy) corals.

 

I had the same problem when I first started and was using tap water. Impurities in the tap water can cause elements including magnesium to precipitate out of the water. I used IO salt and my magnesium was also low.

After switching to RODI water I noticed that the amount of precipitation in my salt water mixing containers was considerably lower than with tap water. IO salt is low in Mg but not 1050 ppm low. My hypothesis is that your use of tap water caused the Mg to precipitate.

As far as getting your Mg to acceptable levels, quite an easy task. However you will also want to monitor and maintain calcium and alkalinity using test kits and additives. Bulk Reef Supply is a good place to start.