Dosing for mag ??

[lluv24]

Hey guys I have a question. I currently have a 220 gallon system. I have a 3 head dosing pump

My current levels are ph 8.3
My kh is 7
My mag is 1180

I've been just dosing the mag by hand with water changes but my levels are not staying at the 1350 range that I like for mag. So I'm going to use the dosing pump. But I'm not sure how much I should dose per day of mag to keep my levels around the 1350 range.

If someone could let me know how much they are dosing with a mixed reef no sps. Mostly lps and nems. Or just how much I should start the dosing pumps at per day would be great. Thanks

[Randy Holmes-Farley]

I'd not use a dosing pump for magnesium since it depletes so slowly. I'd boost it 50-100 ppm per day manually until you reach your goal. Then it should be stable for a long time unless you salt mix drags it down, in which case dosing into the mix itself is a good plan. :)

[thegrun]

I only add magnesium once every two to three weeks...but if you did want to dose, measure your magnesium level, wait a week (no water change in between) and measure again, divide by 7 and you have your daily requirement.

[downbeach]

I have a 180 mixed reef, predominantly SPS, and dose 120mL of Ca and Alk daily, but with regular WC's I never have to dose Mg. Where do you keep your SG? What are you using to measure it with? Even plain IO has a Mg level of ~ 1340 @ 1.026.

[lluv24]

I use Red Sea salt every week water change. My kh is always at 7 sometimes 6.5
My mag is always low around 1100-1200. My salinity is always 1.026

[bertoni]

I agree with Randy. I'd dose the level up to 1275 ppm or so by hand over a few days (to spread out the change), and work from there. Once you get to the target level, testing one or two times a week for a bit should help get a reasonable trend line for automated dosing, if you'd like to try that. Also, a second opinion on any test kit often seems to be useful.

[downbeach]

I use Red Sea salt every week water change. My kh is always at 7 sometimes 6.5
My mag is always low around 1100-1200. My salinity is always 1.026

These numbers are more consistent with a SG of 31ppt(1.0215) according to the Red Sea label. If you know someone with a properly calibrated salinity device, it might be prudent to seek a second opinion before doing a lot of dosing. Assuming the SG is accurate, another possibility is, that you have a bad mix of elements in that particular bucket. There is also some evidence of those elements separating into their elemental grain sizes during shipping, in which case a good mixing of the salt mix might rectify the problem.