Magnesium got too high

Lenny_S · Jan 24, 2016

Hoping I can get a little help here. I use Seachem Reef Fusion 2-part and Seachem Reef Advantage Magnesium dry. While I was out of the country, my caretaker had to mix the magnesium to replenish my dosing reservoir. I did my weekly tests today and my magnesium was at 1600 ppm :(
I asked him what he did and found out he used tablespoons instead of teaspoons. So now I've stopped all the dosing, it seems my Ca and Alk came up a bit too, but those aren't quite as bad. My Ca went from a pretty steady 400 to 440 and my Alk went from a pretty steady 9 dKH to 10.2 dKH. The pH has stayed fine at 8.2 average.
Should I just let it coast back down over time or take more drastic measures? None of the livestock seem to be negatively affected so far. Any advice?

redfishbluefish · Jan 24, 2016

Let it coast back down.......not a big issue.

Randy Holmes-Farley · Jan 24, 2016

I agree. Just let it decline on its own, assuming you do some normal water changes. :)

Lenny_S · Jan 24, 2016

redfishbluefish said:
Let it coast back down.......not a big issue.

Thanks for the reply! How long do you think it might take? i.e. How frequently you figure I should test?

Lenny_S · Jan 24, 2016

Randy Holmes-Farley said:
I agree. Just let it decline on its own, assuming you do some normal water changes. :)

I do, but they are small and I use reef crystals which are already pretty high in Mg. I'm not sure how much of a dent it will make.

Diesel · Jan 24, 2016

How often of a small WC you do??

Randy Holmes-Farley · Jan 24, 2016

How fast consumption uses it depends on how much calcium and alkalinity you are adding. It won't be much more than about 10% of the calcium consumption rate, so even small water changes may be a bigger effect at that calcium level.

One 10% change with Reef Crystals with 1350 ppm magnesium (depends on your salinity, of course) would drop 1600 ppm to 1575 ppm.

That 25 ppm may be as high or higher than your consumption for a month.

Of course, the water change effect peters out as the tank magnesium level gets closer to the new salt water level.

Lenny_S · Jan 24, 2016

I see. I do 5% every 2 weeks. My Ca consumption is 10 ppm per day (that is what I dose to keep at a pretty constant 400 ppm). So by what you are saying my Mg would decrease by 1 ppm per day from consumption and 5% of the delta between the Mg I have and the Mg in the salt mix (12 ppm) decreasing as the gap closes? Do I have that right?

Randy Holmes-Farley · Jan 24, 2016

Lenny_S said:
I see. I do 5% every 2 weeks. My Ca consumption is 10 ppm per day (that is what I dose to keep at a pretty constant 400 ppm). So by what you are saying my Mg would decrease by 1 ppm per day from consumption and 5% of the delta between the Mg I have and the Mg in the salt mix (12 ppm) decreasing as the gap closes? Do I have that right?

Yes, although the magnesium consumption might also be lower if you have corals that use less. That 1 ppm per day is close to the upper limit based on your calcium, but it could be 0.1 ppm per day.

Lenny_S · Jan 24, 2016

Thanks Randy and all. Just a couple more questions... It seems much more Ca will be used than Mg, so I'll probably need to resume dosing Ca much sooner than Mg (probably within 4-5 days)? And should I resume equal doses of 2 part or only Ca if the Alk is still high?

Randy Holmes-Farley · Jan 24, 2016

I expect both will need dosing soon, and I'd restart each when they get to your target levels, which may or may not be on the same day. :)

Lenny_S · Jan 24, 2016

OK, got it. Well being out of the country for 2 weeks and that was the only bad thing that happened. I guess I won't fire my caretaker just yet. [emoji6]

Randy Holmes-Farley · Jan 24, 2016

Lenny_S said:
OK, got it. Well being out of the country for 2 weeks and that was the only bad thing that happened. I guess I won't fire my caretaker just yet. [emoji6]

I lost all my fish one time, and two fish another time. I'd keep the caretaker. :D