It seems there is a bunch of weird input on this thread. for starters, as for your water sorce, getting saltwater for your water changes is fine provided it is a credible store. topping of water with tap water is a mistake, sorry. I would suggest buying either distilled or purified water from the grocery store if you don't have a purification method, or buy rodi from your lfs. your tank probly doesn't evaporate more than a gallon per day so at most it will cost you 50-75 cents per day. also an auto top off is quite important as is a calibrated hydrometer.
As for your water chemistry, your alk is quite high. you would be able to keep it that high as long as you were to keep your phosphate and nitrate from becoming undetectable. no3 ~2-10ppm and po4~.03-.11 if you are carbon dosing and trying to keep a low nutrient level system~no3 0.2-1.5 and po4.005-.02 you will need to keep your alk at a lower dkh ~7-8.5 to keep from having rtn or stn from alk burn aka tissue narcrosis from tips.
once you get everything in range and happy, Stability Promotes Success!
also, good quality GAC would be a wonderful idea to make up for protein skimmer inefficencys. also getting a dark tea collered wet skim is also a good idea while carbon dosing, and don't run GFO if your phosphates are zero
O4-X?
