The goal of the project is to make simple and reliable aquarium fish feeder. The similar project may be found here but it requires special tools and wold take much time. The mechanical part will take about 5-10 minutes. All the parts are rather affordable. Minimum skills required to comlete the project.
Empty plastic bottle with ingector from a medicine.
A piece of aluminium wire 1.7-2mm
Arduino electronics: motor, board, real time clock, display, MOSFET module (not displayed)
Step 1: Mechanics
Using a thin drill make the perforations in the plastic bottle close to the bottom.
Apply another drill with the diameter equal to the inner part of the injector (orange tube)
Apply the above technology to make a perforation in the outer part of injector (transparent tube). The distance from the edge depends on the level of the water and the thickness of the aquarium lid.
Turn the aluminum wire around the thin drill or a steel rod to make a spiral so that it could freely rotate inside of the inner injector tube.
Pull by the ends of the spiral to expand the volutions and attach one end to the motor (e.g. with thermal glue).
Cut the opening in the inner part of the injector so that the nutrition could get to the spiral and insert the tube into the bottle.
Make a perforation in the aquarium lid for the outer tube of injector and assemble the pieces as displayed.
Use a double sided adhesive tape to attach the bottle and the motor to the lid.
Step 2: Electronics
There are plenty projects of Arduino based alarm clocks which can be used to turn on the motor for several seconds once or twice a day. The main empasize of the project is on the mechanical part, so perform the electronic part depending on your needs. Just keep in mind that the output current for Arduino pin is 40mA so use a MOSFET module or a relay module to power up the motor.