Your Ph needs to be brought up to 8.2 at least, and your alkalinity needs to be around 3.75 to 4.75, and your dkh 9 to 12. The water changes will lower the nitrates initially but they will come back up until you do water changes for a few weeks and only if you take out more than you are putting in. On the salt, you can either change your salt, or, if you are using r/o water you can use an r/o water reconstituter such as OSMO prep by Kent to give you a better base for mixing your salt and to help keep your Ph and alkalinity up. good luck hope something here helps. (an item overlooked a lot of times, Magnesium? Make sure your magnesium is at proper levels.)