Chillquarium is an idle game where you load it up every day for 10 minutes, sell duplicate fish, and then close it. The fish are static pngs that float around the tank towards your cursor. You can buy more and bigger tanks, as well as static pngs to add as decoration.
This game added nothing to my day every day and I kept playing it for a few months because it was just 10 minutes a day and it wasn't offensive or anything but I don't think I will ever think of this game again after uninstalling it.
There is nothing here for you beyond just something to kill 10 minutes a day. It is a game that won't surprise or engage you. It's not meant to do that, I guess, but I imagine that if the fish were actually animated or the mechanics were in any way interesting I would feel rather positively about the game.
I don't wanna be mean to the game, but it feels like the design document began and ended with "chill vibes". There are too many small problems with the game - fish feeding barely works, the game has no sell duplicates button, the value tab constantly bugs out and displays incorrectly - for it to be this simple. You could do worse, but cookie clicker is free.