Mg/Ca/Dkh - how much to move and how fast?

[PSU_Reefer]

Hey all,

so i've been testing dKh for a little while and have it right around 8.0. I just tested my Ca and Mg levels and both seem low:

Ca - 310
Mg - 1170

I have the aquaforest Ca and Mg plus solutions and the amount they say to add looks huge. how slowly should i be bringing this up? do i need to adjust Dkh with it?

Thnaks

 

[Randy Holmes-Farley]

Those levels may imply low salinity as a cause.

What do you think the salinity is and how are you measuring it?

 

[PSU_Reefer]

Those levels may imply low salinity as a cause.

What do you think the salinity is and how are you measuring it?

1.024/30% using the BRS refractometer

 

[Randy Holmes-Farley]

1.024/30% using the BRS refractometer

Calibrated how?

30%? 30ppt is not a sg of 1.024. It's more like 1.0226

If we assume 30 ppt is correct, then you can raise the calcium and magnesium levels quite a bit by boosting the salinity to 35 ppt

Ca - 310 --> 361 ppm
Mg - 1170 --> 1365 ppm

 

[PSU_Reefer]

Calibrated how?

30%? 30ppt is not a sg of 1.024. It's more like 1.0226

If we assume 30 ppt is correct, then you can raise the calcium and magnesium levels quite a bit by boosting the salinity to 35 ppt

Ca - 310 --> 361 ppm
Mg - 1170 --> 1365 ppm

ahh ok thank you. i'm not sure how my salinity drifted down. you are right. i'ts about 1.0225.

so you would recommend just doing a water change with a slightly higher salinity to raise it up?

 

[Randy Holmes-Farley]

ahh ok thank you. i'm not sure how my salinity drifted down. you are right. i'ts about 1.0225.

so you would recommend just doing a water change with a slightly higher salinity to raise it up?

I'd replace evaporated water with salt water until you get to the target.

 

[PSU_Reefer]

I'd replace evaporated water with salt water until you get to the target.

Thank you!!

 

[Dkeller_nc]

Yep, that's the easiest way, especially if you have an ATO. If you do, I'd suggest putting half-and-half correctly adjusted ASW and RODI in the ATO reservoir, and just measure your tank's specific gravity over the next several days to determine when you need to switch back to just RODI.

 

[Bodyguard]

You could also overfill your sump return section with slightly elevated salt levels so your ATO isn't kicking on to maintain your current salt level. I found this works great as it slowly raises the salt levels and your ATO pump isn't having to process salt. Keep filling the return section until the desired 35ppt is achieved.