Dosing nitrates is adding liquid poop. Why not get something out of your liquid poop and have a fish to watch make the poop. My dad has a 12” v. Tang that would do a pretty good job helping your nitrate issue ;Hilarious
Say you are treating a SPS tank for ICK and need to keep it fallow for 79 days. You may want to add nitrates using additives. There may be other reasons as well for SPS coloration and health you may want to test out higher nitrates in a short time interval. If you don't like the SPS or tank response, can stop dosing instead of relocating a fish.
Also with a proper quarantine procedure, new fish would not go into your tank for atleast 14 days.