let me see if i get this right.... mag ?

[am3gross]

i just did a test on a fresh batch of saltwater that was made up last night. the salt used was instant ocean. did a mg test and it was at 1180. now i know that i want this to be around 1300.... if i wanted to bring the mg level up i could use an additive and add it straight to the just mixed saltwater correct? so instead of adding to the tank and all 400 gallons that i have then i only have to do it for the fresh saltwater that i will add to the tank. does this make sense to any one?

[reefnetworth]

thats what i do, your Mg should be 3X's the amount of your Calcium.
I.E., 450ppm Ca = 1350ppm Mg

FWIW, i use Kent Tech-M, its cheap and its pre-mixed. other than that one supplement, i use Randys' #2 recipe (reef chemistry forum).

[am3gross]

ok i just mixed some of the supplement that i have which is kent liquid reactor. i added 2 cap fulls and it raised the mg to about 1340.... some where in there. the amount of water was a 30 gallon trash can.
i will do a calcium test now to see where that is at. thanks for the quick reply!