Make it controller ready and your golden!
I've been using a synchronous DC motor in the ~3rpm range and then gearing it down to turn the feed mechanism at about 1 rpm. It's the same kinds of motor used in many of the peristaltic dosing pumps.
It feeds a fairly consistent inch or so of nori into the tank per minute of running. The power supply is simply plugged into the controller and set on a timer. Nothing is directly measuring the nori fed in, but it consistently feeds in the same amount of nori for a given amount of time run.