If your using a water holding tank then you dont really need a carbon filter either. Just top up the water holding tank when necessary and add some neutraliser. Alternatively if you already have the carbon filter I would remove the water holding tank and just drip straight from a dedicated water tap (via carbon filter) into tanks. I drip directly into my tanks without a cabon filter but my tanks are larger. In a 72 hour period, the amount I drip in compared to tank volume is about 10% so a tiny amount of chlorine is okay.
If your stuck for a small water tap, just use airline hose and airline taps. I use them to feed infusoria 24/7 to fry tanks.
Thanks for the metaphor, it is just that I grew up dealing with electrical and electronics. The closest I have done plumbing is using a python to do water changes...
The idea here is to make this maintenance-free as possible, which you have suspected. It is also to make everything localized to a desktop or nightstand in someone's office or bedroom without piping to the nearest tap source or drilling through a wall.
So in essential... you have a portable constant water changer that keep the water parameters stabilized as much as possible which only need topping off.