This is incredibly enjoyable. I wishlisted this on Steam. My only suggestion is to add more music options. There's lots of really good atmospheric ambient relaxing songs for free on the internet. I love the style. I suggest adding an option for Thunder and Rain coming every 10 minutes and raining for 15 minutes then stopping, a little popup text should say "rain coming in 10 minutes" then "rain coming in 5 minutes" . and the fish grow 10% or faster during the rain.
Viewing post in Tranquil Koi 鯉の池(DEMO) comments
Thank you it's really encouraging me when I was reading your comment! I would definitely add more music options, maybe also unlockable music packs in the game. A weather system was also one of the ideas I was considering when I was building the game at first but I cut it due to its complexity that time, maybe I will consider to add it back!