I have a Hydor fish feeder, EBay about £20 10 years ago. Works fine on my Juwel Vision 180, which I had to make a cutout for the feeder in the top flaps.
Runs on 2 x AA cells, which lasts months and months and months. Can set to one, two or three feeds a day. Also got an air line in to blow air through the food to stop it getting damp.
I use a £1 Ikea pestle and mortar to crush up fish food (flakes, JBL catfish food, algae flakes etc) so all bits are small enough to pass through the opening. Can set opening size to control amount of food dropped.
Use it all the time now.