Aquaponics - String feed counter

The small volume of the food that's being dumped each time my on demand feeder triggers makes it difficult to measure, so I've been trying to figure a way to register trigger events.

My fist attempt at measuring the times when my fish triggered the feeder was a small spot of blutack on the top of the shaft. If the shaft moved while I was away, I could tell. But it turned out that the shaft turned one full revolution on at least one occasion, so there was no way of know if the fish had triggered it or not because the blutak was right back to where it started.

The next was a small pebble that I could leave sitting on the top of the shaft. If triggered, I would find the pebble lying next to the shaft. This worked but could only measure one trigger event before I would need to notice it, and reset it.

My latest design is a piece of string attached to the shaft, with a nut on the end for a weight. When the fish trigger the demand feeder, the string winds around the shaft, and raises the nut up.

It wont tell me exactly how many times it was triggered, but will give an indication of how long the motor ran in the time since I last reset it. Each time the fish hit it, it seems to turn approximately one revolution, so I should be able to mark off a rough guide on the wood. This should make a reasonable gauge to tell me how active the fish have been in setting off the feeder.