bettas usally take a day or so to get used to the tank (at least mine did) after that they would swim around and be active
any way dont try feeding him the first day bcuz he probly wont
how big is the tank? Does it have a heater?
water parameters? (nitrate, nitrite, ammonia) tested wiht a liquid test kit
did you use declorinated water and let it sit for a day before throwing in the fish?
to help us help you, can you answer those questions.
the tank is 2 gallons and it doesnt have a heater
i did dechlorinate the water and waited a day before putting him in there
but i dont know the water parameters.
i got him monday and hes still acting weird.
right now hes just floating at the top of the tank
as said, the mini heater is needed for the smaller 2gal. and most lfs carry them
i would also suggest a liquid test kit. so you can test the water regulary
as for the fish, i had one just like that, research said he had a swim bladder problem or constipation.
have you tried feeding him yet? what kind of food? if he is not laying on his side it is probly due to the lack of heat bcuz they get much more active in the right temperature