Considering what's in your tank, most of your issue will be with the salmix depending on how often/how much water changes are done. Scleractinians and heavy coralline growth are your main draws on CaCO3
The first goal should be to re-balance your chemistry. It would be much easier through a series of water changes once you tweek the IO with some Turbo Ca
. Need you to post the numbers of a new batch after mixing for 12ish hrs and the water volume used before doing any "tweeking". Chemistry additions should also be done after the 12 hour mark to be sure it does not cause abiotic precip.
If not, you can easily add 1 tspn of Turbo Ca
pre dissolved in your top off water each day for 7 days. If will bring it back up towards the 400-410 ppm
level. At the same time, you need to let the alk
fall to about 7 DKH
. This would put you in a much better balanced region. You will still need to figure out the balance on your saltmix or this problem will re-occur with future water changes.
Once the main tanks balance is accomplished, the next goal is testing every second day or so to plot the rate of depletion. Make sure no water changes or additives are used for a good 6 days. So basically test Monday, Wednesday and Friday. You'll be able to see from the first test to the last a total net change in your chemistry and give you a better idea each days approximate usage. You can then target the amounts needed each day with much more accuracey. Once you have a additive schedule plotted, you can ease off testing to weekly at first to confirm the additions are working and augment where needed. After a short time, monthly or twice monthly testing will be all that is needed unless coral additions are made that might change the equation.
As far as your Majano problem... http://www.joesjuice.com