Originally Answered: My Betta Fish!?
its flaring at you bcuz its angry about being in a bowl. heres why bettas (or any other fish) should not be in bowls:
no heater-bettas are tropical so they sloooow down because they are cold, bettas are way more exciting in a heated tank, mine is in a 30g heated, filtered etc community tank and she is all over the place
temperature changes a lot between day and night, it isn't constant, and that stresses the fish
no hood, the fishy might jump out, also things can fall in the water
no filter, ammonia from waste gets higher and higher while uneaten food falls and rots on the bottom and uncontrolled algae dominates the sides, ammonia spikes and if the water is not changed often, can be fatal to the fish
the warped sides of the bowl can cause the fish to go blind
boring!! no space to move!! all the poor, cold betta can do is sit in his own waste and stare out the warped sides of the bowl and imagine the luxury of a heated, filtered 5g!!!
and he probably sees his reflection and it looks all funny cuz he's in a bowl. bettas like blood worms, anything freeze dried, i feed my fish twice a day (there are 11 others besides the betta) with flakes, spirulina, and blood worms and they go crazy for the blood worms.
bettas aren't aggressive, they are just misunderstood. males fight males, also sometimes angelfish and male guppies.