Low Alk and Cal

[mooshoo62]

Hello,

I've recently started testing for Alk, Cal, and Mag after cycling my IM 75EXT. Tank is 2 months old.

To my surprise, despite using Coral Pro salt, my alk and calcium were down at 5.7 and 360 respectively. I've since started testing the water parameters of the water going into my system before water changes, and have found the levels to be where I want them. After performing water changes I only saw a slight bump to alk and cal, which was expected, but within a day or two they were back down to the original levels.

I have nothing in my tank except for newly cycled macro rock, 80 lbs of live sand, some fish, CUC, a cleaner shrimp and a BTA. I have no coralline growing yet and just a small diatom bloom.

In order to raise the parameters, I installed my DOS and started dosing 10ml of each part on alternating day/night schedules. This has helped stabilize my PH a bit, but after 3 days, has had little to no effect on my parameters.

Alk - 5.7
Cal - 370
Mag - 1140

What could be making this happen?

Thanks,

 

[Jekyl]

Have you double checked your testing? What tests are being used? All numbers being low could point to an error in salinity.

 

[mooshoo62]

Have you double checked your testing? What tests are being used? All numbers being low could point to an error in salinity.

I thought the same thing and even went as far as buying new refractometer calibration solution, and then taking a sample to LFS to be double sure it wasn't by refractometer.

All readings are stable at 1.025

 

[mooshoo62]

Have you double checked your testing? What tests are being used? All numbers being low could point to an error in salinity.

Also, I am using salifer, but also went to lfs and they used the red sea kit, and it was within the same general low ranges... I'm fairly certain it's not the test equipment, but I could always use an excuse to buy more hanna checkers...

 

[mooshoo62]

@Randy Holmes-Farley

 

[mook1178]

I would venture to guess you have temp issues using a refractometer to get the correct salinity. Get a salinometer from Hannah, and actually measure salt and not density.

 

[Biokabe]

From a chemistry standpoint, the only explanation I could think of would be your calcium/alkalinity precipitating out of solution. I couldn't venture a guess as to what would cause that, but from my poor understanding of the chemistry I wouldn't think your levels are right for that. You don't really have any big users of cal/alk.

One (physical) explanation could be that you have a slow leak somewhere in your tank or your plumbing. So you're losing saltwater, and replacing it with freshwater, especially if you have an ATO. This would result in the lowering of both your salinity and anything else in your water (such as alk/cal).

That would be a LOT of water lost to make that big of a change though, enough that you should have noticed it unless your tank is set up such that water either drains or evaporates before you have a chance to see it. Still, if it were evaporating you would still expect to see a pile of salt crystals all along your floor/interior of your stand.

 

[mooshoo62]

I would venture to guess you have temp issues using a refractometer to get the correct salinity. Get a salinometer from Hannah, and actually measure salt and not density.

Is this what you're referring to?

Marine Salinity Tester - HI98319

Hanna Instruments HI98319 Marine Salinity Tester measures conductivity (EC) to determine the salinity of natural and artificial seawater within seconds.

www.hannainst.com

 

[mooshoo62]

From a chemistry standpoint, the only explanation I could think of would be your calcium/alkalinity precipitating out of solution. I couldn't venture a guess as to what would cause that, but from my poor understanding of the chemistry I wouldn't think your levels are right for that. You don't really have any big users of cal/alk.

One (physical) explanation could be that you have a slow leak somewhere in your tank or your plumbing. So you're losing saltwater, and replacing it with freshwater, especially if you have an ATO. This would result in the lowering of both your salinity and anything else in your water (such as alk/cal).

That would be a LOT of water lost to make that big of a change though, enough that you should have noticed it unless your tank is set up such that water either drains or evaporates before you have a chance to see it. Still, if it were evaporating you would still expect to see a pile of salt crystals all along your floor/interior of your stand.

Thanks for this. I put a small pump in the return chamber to hopefully avoid any precipitation but still having the same issue.

I don't have an auto draining system and the floor is dry so we can rule out the leak... thankfully.

I started dosing Mag to get that up closer to desired levels. LFS thought this was typical for new tanks and getting up the mag would make raising the ALK/CAL easier.

 

[Randy Holmes-Farley]

I would venture to guess you have temp issues using a refractometer to get the correct salinity. Get a salinometer from Hannah, and actually measure salt and not density.

Just to be clear, Hannah’s meter measures electrical conductivity, so it is measuring a physical property of the water just like a refractometer or a hydrometer.

 

[Randy Holmes-Farley]

Thanks for this. I put a small pump in the return chamber to hopefully avoid any precipitation but still having the same issue.

I don't have an auto draining system and the floor is dry so we can rule out the leak... thankfully.

I started dosing Mag to get that up closer to desired levels. LFS thought this was typical for new tanks and getting up the mag would make raising the ALK/CAL easier.

I see no reason to think magnesium is low in new systems, if that is what you mean. Precipitation on bare calcium carbonate rocks and sand in common in new systems.