Mg and Ca undetectable, even after water change

[Hoochee]

~23 gallons of water

5 months old

wave makers on opposite ends of tank

HOB CPR 3.6g refugium w about a tablespoon of chaeto and several fronds of Caulerpa, life rock rubble, IV sterilizer

2.5” Niger trigger and 6” snowflake eel (both eventually moving to a 75g tank so no hating)

one small frag of Waving Hands Anthelia. So small the hands almost can’t be seen

Nassarius, Trochus and Astraea snails

1.026 salinity
8.1 pH
~3 Nitrates
<1 Phosphates
8.2 Alk
Undetectable Mg and Ca

Salifert test kits, retested Mg and Ca with Red Sea kits - Same results

that last one is a new problem I found Tuesday this week. Until then both were pretty consistently mid 1300 and 400, respectively.

I did a 15-20 water change Monday, so day before testing, another today. Tested a few hours after the water change today and still undetectable Mg and Ca.

Tested the newly mixed water [IO Reef Crystals] and found acceptable params [a little low on Mg and Ca so now I know how it mixes].

it seems unlikely there’s macro algae to be siphoning off all the Mg and Ca but I’ve attached a pic.

Thanks in advance for thoughts

 

[Randy Holmes-Farley]

How was this water made?

There is NO normal way to remove all calcium and magnesium from seawater in a normal aquarium.

 

[Randy Holmes-Farley]

I’d reread the test kit directions, and test new salt water and tank water side by side.

 

[Hoochee]

Agreed.

Made it the same way and with the same bucket of reef crystals I’ve been using for 5 months-

RO/DI w 1/2 cup per gallon of salt

to clarify - the new fix is ok.

 

[Miami Reef]

I was like, “Whaaaaaaaat?!?” when I read the title.

Definitely never heard that before!

 

[Hoochee]

I’d reread the test kit directions, and test new salt water and tank water side by side.

Although I’ve used the same Salifert tests for 5 months I have re-read the instructions, in fact I read them every time I test. Also looked to make sure I didn’t mix the reagents or other components between kits. The potential for a bad test method or kit is why I also tested with a Red Sea kit.

 

[Hoochee]

Just went next door and got water from a neighbor’s tank. Same kit, same method, same person testing (me).

Result = ~1260

Didn’t check the other Ca since I’ve confirmed it’s not a Mg test fault.
Not kit, user or method issue.

 

[taricha]

Just went next door and got water from a neighbor’s tank. Same kit, same method, same person testing (me).

Result = ~1260

Didn’t check the other Ca since I’ve confirmed it’s not a Mg test fault.
Not kit, user or method issue.

When you say your water has "undetectable" Mg and Ca on a titration kit, do you mean that it never changes color? Because if so that doesn't mean the Ca and mg is zero. It means it's out of range high for the test kit. You ought to be able to add more titration drops and achieve a color change to give you an estimate of how much out of range High you are if that's the case.

If you mean undetectable, as in literally the titration step goes to the endpoint color at the very first drop, then you should taste the water and see if it's actually salt water or use a hydrometer to measure salinity and figure out how your entire system got replaced with fresh water.

 

[Hoochee]

When you say your water has "undetectable" Mg and Ca on a titration kit, do you mean that it never changes color?

I was just coming back after realizing my stupid choice of words - both are out of range.

refilled the syringe. Looks like Mg is about 1600.

let’s pretend I was never here.

 

[taricha]

let’s pretend I was never here.

You aren't the first and won't be the last to confuse us this way.

I was secretly hoping for an elaborate story about an undetected leak and a monster top off system that quietly replaced your entire tank with RODI. But this is a much better outcome for your tank.

 

[Randy Holmes-Farley]

Glad it’s worked out!