Great homage to Insaniquarium and evenly addictive. I couldn't figure out a lot of those fishes yet, for example my aquarium was flooded by pills no one wanted to eat and that blue fish didn't want to eat anything yet. I just refreshed the browser window and saw that there are other kinds of fish - are those random? So maybe I got combinations that don't fit well together?
I think the core gameplay loop and mechanics work great. I would've liked it more if the other kind of fishes were gradually introduced, instead of unlocking them all at the start. Maybe that way it would be easier to learn what those fishes like. In my opinion it's great that you don't have something like those pesky aliens attacking now and then like in Insaniquarium, those were really stressful. On the other hand I missed those little helpers you could get after some time, e. g. the snail to collect coins or I think there also was some auto feeding mechanism.
All in all great entry with lots of potential to build upon.