Friday, March 6, 2009


Chemistry was never my strongest subject in high school or college. I was much better at physics, calculus, statics and dynamics, etc... For some reason chemistry and I never had a really great relationship. Don't get me wrong, I got by. I believe I got a B in college chemistry but it wasn't an easy B. It was a struggle. Somehow, after all these years, I still remember that Avagadro's Number is 6.02 x 10^23 and that it is the number of atoms in a mole. Not sure what to do with it after that though.

So, lately, I'm wishing I remembered more about chemistry. I'd like to have a better understanding of the relationship between alkalinity, pH, calcium and magnesium. I have been using two-part additives and supplementing calcium and alkalinity. I stopped dosing calcium because I was pushing 500 ppm in my tank. I now just let the level drop between water changes. I'm measuring the calcium level of Coralife salt to be 540 ppm. Doing water changes every two weeks seems to be enough to keep my calcium level between 440 and 460 ppm. Right after a water change the level is 460 ppm after two weeks it drops to 440 ppm. I'm kind of surprised it only drops to 20 ppm. I expected my calcium consumption to be higher than that.

I have found that I need to continue dosing alkalinity. In the same time period my alkalinity has dropped from 3 meq/L to 2 meq/L. During this time I have been dosing but apparently not enough. My pH seems good. Last night it was at 8.15.

Over the last few weeks I dosed magnesium bringing my level up to 1275 ppm. I measured the magnesium level of Coralife salt to be 1335 ppm. I haven't been monitoring magnesium long enough to know how it reacts long term. However, since sea water has a magnesium level of about 1250 ppm there is a chance that the additional magnesium in Coralife salt will replenish what is consumed by my corals and coraline algae and keep the level at an appropriate level.

Here is a good article I found about reef chemistry. It provides instructions on how to adjust calcium and alkalinity levels.

I've almost used up all of my alkalinity mix. This time instead of buying it I'm just going to use baking soda and see how that goes.