Still though, don't you get a build up in the total dissolved solids in the water?
*Fish waste will be pickup by filter and bacteria that holding nitrate by protein skimmer (strong protein skimmer is a must and strong/turbulent circulation is recommended for carbon dosing) so no waste sitting on bottom or just vacuum those waste out that collected at some area in tank.
*You will have to dose minerals daily or weekly that loss cause no water change (top off with fresh water that loss cause evaporation, or salt water if your salinity went down).
Notes:
There is a risk with carbon dosing that if you don't have enough circulation your live stock will die due to Oxygen got depleted by massive bacteria army. If you power out and you're not home for long time then probably you looking at a possible wipe out entire tank so setup some sort of battery back up to provide enough Oxygen for your live stock during power outage.