Missing Magnesium!! Please Help!

[BerndtSea]

We have a 75 gallon tank with a Fluval 407 cannister filter.
Bottom tray-black sponge followed by polyfill,
Second tray- Chemi-pure & polyfill.
Third level- biomedia.
Final tray- ZeoCarb & phosphate remover pads
Return line has a fluval spray bar, the Inlet has a Fluval skimmer with midline filtration
Lights- two Ai prime Reef HD set at 6” from glass top
Also in line is the Fluval UV sterilizer set to run 24 hrs
Corals; Zoas, Purple headed hammer, Kenya tree, Cloves, Waving hand Xenia, Green tipped Anemone
Stock; Coral Beauty, Six line Wrasse, Green Mandarin, One mocha storm, One snowflake clown, Aiptasia file fish, Watchman Goby, Pistol shrimp, Fire shrimp, Cleaner shrimp, emerald crab, Handful of Trocus Snails and bue legged hermits, Two conch snails, one tuxedo urchin
Now here’s our problem, we noticed our corals all shrinking, almost appearing as if their growth has been massivley stunted. Our parameters today were:
Alk- 8.3
Cal- 400
Mg- 1050
N03- 40
P04- .5
Sa- 1.023
PH- 7.8
We added 16 ounces of the fluval magnesium additves to get it to just 1050. In between dosing we noticed the next morning the magnesium would tank again down into the 800’s. Today we switched over to the ESV B-ionic Magnesium and dosed 200ml. We went from 860 to 1050 after adding it.
We aren’t sure why our magnesium was leaking out in the first place, and even more unsure now what could be happnening to keep it so low. We could really use some help here before we lose our corals.

Our secondary, and smaller issue, is the Salinity. Earlier today we had a test down with our water by a LFS, she gave us back these parameters;
Alk- 8.1
Cal- 370
Mg- 850
N03- 37-38
P04- 1.5
Sa- 1.015<<<<<< Here’s our question on this one, would anything even be able to survive a salinity that low? We are really hoping it’s thier calibration and not ours.
We appreciate any help/advice we can get here. We are stumped as to how wee could addd this much magnesium nad our corals are still acting this way, and the test reading low. We hope we offered all the information needed, feel free to ask any further questions, thank you for all the expertise!!!!

 

[cooltowncorals]

Test the salinity again see what you get

I would think your inverts wouldn’t like salinity that low and would all die relatively quickly

the fish yes there are lots of fish stores that keep low salinity to repress parasites. Like 1.020.

I don’t know for sure about 1.015 but I would assume it’s bad for all, but fish could probably live for a while.

if your salinity is super low it would lower your magnesium as well.

how are you topping off your aquarium?

how confident are you in your refractometer?

 

[BerndtSea]

We aren’t very sure, We use calibration fluid and it goes to 35 ppt and stays there. We are considering getting a new one to triple check as our Inverts are all happy and alive. We top off with RO/DI water testing at 0 tds whenever its below our fill line and never fill above our marked point. 20% water change two days ago but our tank has taken that just fine each time before.

 

[Garf]

We aren’t very sure, We use calibration fluid and it goes to 35 ppt and stays there. We are considering getting a new one to triple check as our Inverts are all happy and alive. We top off with RO/DI water testing at 0 tds whenever its below our fill line and never fill above our marked point. 20% water change two days ago but our tank has taken that just fine each time before.

I think you need to make some calibration solution for your refractometer;

http://reefkeeping.com/issues/2004-06/rhf/index.htm

 

[Randy Holmes-Farley]

The salinity is not sg = 1.015 unless you have added a lot of calcium or the calcium value is in error.

If you boost the sg from 1.023 to 1.0264 (35 ppt seawater), magnesium will rise from 1040 ppm to 1194 ppm.

Magnesium testing is also OFTEN inaccurate. If you have not been adding a lot of alka nd calcium, I'd ignore it. It will match the salt mix and is very likely fine.

 

[BerndtSea]

This morning our magnesium was 1200, cal was 380, salinity was 1.023, p04 was .25. We added 40ml of calcium and 200ml of magnesium. Our Ph is at 7.8, should we raise that to 8.4 and what should we use? Should we also keep raising our magnesium to 1400-1500? Again thank you for your guy’s help, our corals are looking a little better today.

 

[Randy Holmes-Farley]

This morning our magnesium was 1200, cal was 380, salinity was 1.023, p04 was .25. We added 40ml of calcium and 200ml of magnesium. Our Ph is at 7.8, should we raise that to 8.4 and what should we use? Should we also keep raising our magnesium to 1400-1500? Again thank you for your guy’s help, our corals are looking a little better today.

I'd boost the salinity first.

Your target magnesium is certainly a viable opinion, but I do not agree that it needs to be so high. Organisms thrive in the ocean at 1250-1350 ppm magnesium.

 

[BerndtSea]

UPDATE: we bought a new refractometer and tested. Our salinity is in fact at 1.015!! No idea how anything is alive. We are going to bring it up slowly but as fast as we can if that makes sense. Any guidance would be so helpful!!!!!

 

[Randy Holmes-Farley]

Are you sure? How did you calibrate the refractometer?

This is a bit of an issue now because calcium and magnesium are going to get very high if you raise the salinity. Calcium will be over 700 ppm. Unless you added calcium, it doesn't make sense.

Have you been adding calcium? If not, I definitely would not raise the salinity that much without triple checking the salinity.