Here is a cheap alternative you can make in a few minutes without electronics knowledge.
Step 1: Materials Needed
1 Small plastic can (must be light weight)
2 Thin neodymium magnets
1 Plastic pen or plastic tube
Step 2: Tools Needed
1 cutter knife
Some instant glue like cyanoacrylate
Step 3: Preparing the Clock
Proceed to dismount the clock case for removing the front (transparent) cover.
Once you remove the transparent cover, mount again.
Carefully remove the clock hands pulling them slightly towards you, one by one.
Step 4: The Timer
- Sandpaper the the tube to make a perfect cylinder.
- Put the cylinder on the exact center of one magnet and drop a glue drop inside to paste both parts.
- Roll a piece of fine sandpaper and put it into the cylinder.
- Sandpaper turning inside the tube and check until the piece fits perfectly on the outer gear piece (where the hours hand was)
Step 5: The Automatic Food Dispenser
- Make a square of about 10mm on the can and cut it. (Better if you heat the blade of the knife to avoid cracking the plastic)
- Draw a 30x30mm square on a cardboard and cut it making a cross.
- Bend the tabs as shown in the picture and paste with adhesive tape to make an opened box
- Paste the box with adhesive tape by the outer lid inside the plastic can.
- Remember that the hole of the box should go clockwise to let the food go by.
Do not glue the box tho the plastic can, maybe you'll need to make a different size one in the future. Use adhesive tape to do this.
The bigger the window and the box are, more food will fall.
Step 6: Finishing the Project
- Open the plastic can and fill it with your fish favourite food (then close it).
- Take the clock and the plastic can and let the magnets do their work...
Now the clock will drop a bit of food each 12 hours (when the window is at 6 o'clock).