When we go on vacation, for example now with the bridge or aqueduct that exists in Spain and that allows families to rest, hopefully, a whole week of vacation, the fish is not one of the animals that we usually carry with us, aquarium included, to be able to put it where we are for a few days to, on the way back, do the same.
What is usually done is to leave food for them to eat, but it is not the normal food that we give the fish daily but can come in the form of tablets so that it dissolves little by little and, in this way, they always find food. that they need it.
These food pills they can be found in stores and are intended more for when we go on vacation. It does not mean that you cannot feed them with them but keep in mind that the food is pressed and the taste is not as pleasant as if that food is loose (also, some even have a predilection for a food color; if you have not noticed watch when they eat what they do if they eat something they don't like and go for a different one).
The pills usually have different duration. There are them for weekends but there are also other larger pills that can serve longer. If you do not know, it is best to ask one of the managers of the store. Its price also varies according to the brand and size of the pills.
Even some stores, or some hobbyists, make their own inventions (such as automatic dog feeders) that dispense daily food. Of course, for fish it is a bit more difficult to do, but it can be done.