Could be a bacterial infection called Popeye.
Probably due to poor water quality.
Filter a fish? Do you mean filtering a fish's tank? Well you have to filter any fish's tank.
It means there is a bulging between the 6th and 7th vertebrae in the neck (cervical part of the spine).
That is just the color of your fishes scales,it does not really mean anything, why do some people have blue eyes and some people have brown eyes its just a distiction of that fish.
Coy fish are said to be good luck symbols. They also represent fortune and favor in many people's eyes. The coy fish is a popular positive symbol.
It is black on it's back and on it's beak and is white on stomach and around eyes and stands 1 1/2 feet tall
It means he hates you. Bettas flare their gills out when they're trying to scare another betta away, or to impress a female with how large he is.
I am not sure what you mean by "spread your eyes." If you mean to move location the answer is no.
For your eyes
yes,all animals sleep,just because fish don't blink doesn't mean that they don't sleep.If you think they don't sleep because they don't close their eyes, well they don't close their eyes because they have no eyelids.Therefore they can't close their eyes even if they tried.
I Believe You Mean Cuttle Fish...
eyes
The fish is larger.