Here is the automatic fish feeder that I like. They are fairly in-expensive if you buy them at Wal-Mart, usually between $10 and $12. Don’t get them at a petstore as they are usually $25 to $30! All they are is a Quartz Clock movement that rotates a feeder drum. The will feed the fish 2 times a day, 12 hours apart.
Here is an exploded view of the feeder. You can see the clock movement in this photo. You can also see the blue clutch mechanism that allows you to set the “time” that you want the fish to be feed.
A close up of the clutch. You can adjust the time of the drum to within 5 minutes.
My plans are to tear this thing apart and replace the clock movement with a RC hobby servo. By using a servo and a controller, I will be able to feed the fish when I want. My personal belief is that fish would be happier if feed less more frequently. I am a big critter, and I like to eat more often then 12 hours apart. How do you think the little critters take to it? 
