Depends on the water volume you have. For me, raising it by 100ppm per day was about 400-450ml of Mag solution. You can do the calculator on BRS, or use the one below. Make sure to subtract the volume for rock, equipment, etc. For example, my display is about 60 gal, plus my 20 gal in the sump, plus my 25 in frag tank...but I calculate on 75 gal.
As you go up in Mag, obviously you'll need less as you get closer to your target range. Its generally best to not raise Mag by more than 100ppm for a single day.
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Yea or alk by 1 DKH or cal by 50ppm. Also he is running a 28G sp raising somthing in there shouldnt even need that much maybe a wayer bottle or so. Water bottles are 500ML i know that by heart lol