There is a method stocking aquarium in some cultures around the world called "pickerel stock tank", the tank heavily stock to create a crowded look that almost no space to swim for each fish and the owner love it like that, despite the crowded look these tanks have extreme excellent filtration and animals that live in there are well taken care of by the owner.
*I've seen a 300G tank with another 400G filtration system so the total water volume is 700G, it's bad if you only look at what you seeing in front view and behind the curtain/wall is another different story.