Originally Posted by clopez1
The single betta thing I understand because yes they see another betta but how do fish know how many are there? Lets say you're swimming in a circle and we all look alike..How do you know how many people are there? You pass the same fish maybe 20 times, can they recognize each other to the point where they can say well there are only such amount of us? Not sure if that made sense but..The game is starting!
I'm not sure what the logistics of it are, but I think that for shoaling fish they don't actually count, they just instinctively feel safer in a group of 5 or more or whatever the rule is because that's how they know how to survive. Safety in numbers and all that. The more fish there are, the less individuality there is. So a fish that feels sufficiently part of a group just needs a specific minimum amount of fish to know there is a small chance of it being singled out by a predator as long as it blends in with the others.
Tangent: I've also read that scientists have been able to get robotic fish accepted as part of a group as long as they're the right general shape, size and color and behaving like the other fish.
Another consideration is that territorial fish need a certain amount of space in a tank to get along with other fish of the same species. So their territory size in the wild needs to be mimicked in a tank, meaning that if a fish needs X amount of gallons for territory, you divide the total number of gallons in a tank by X to see how many fish of that species you can comfortably keep. Usually these rules are bendable, especially in a heavily-planted tank with the line of sight sufficiently broken up.