Although it does depend on the type of fish you have, nearly all fish can safely go 3 days without food. I bought EHEIM Everyday Fish Feeder last month, and it works pretty well. And I can leave home couple days without worry or bother someone to feed my fish. But when you do remove the batteries to turn it off, you will have to reprogram it again.
We have tested this setup for more than a week with us gone on vacation. The only extra maintenance for us upon return was to catch up with a water change and clean the glass. I think it probably overfeeds a bit, but I don’t expect operation from a machine that is as intuitive as I am with feeding.
It’s easy to program and can be mounted to the top with the included bracket or on the side of your tank with a strong sticker. Auto feeders vary widely in their ease of use, and some are a lot harder to program and operate than others. Premium models may have digital displays, while the フードタイマー analog types often resemble an old-fashioned light timer. I’d definitely prioritize getting a model that’s easy to use and adjust, but whether you go digital or old-school is a personal choice. The other limitation is that most feeders can only hold and dispense a single type of food, which may not work for more diverse communities. You are actually the second person here to suggest using a Grasslin automatic fish feeder.
But you cannot expect it to perform as well as a good fish feeder you buy from a store. First of all, you cannot really control the quantity it drops into the water. Secondly, it only works with certain types of fish food, granules, and pellets. And then, there’s the aspect; you may be proud of your homemade automatic fish feeder, but it won’t look pretty hanging over your beautiful aquarium.
Maybe you have top feeders that do fine with pellets or flakes, but you also have bottom feeders that need algae wafers. I should mention here that the success of your fish feeder depends a lot on the type of food you use. The Fish Mate F14 has a simple air pump hose attachment on the bottom. The IntelliFeed Fish Feeder has a drum that sits inside a housing. To dispense food, it moves out, rotates, and then moves back in.