Fantail Goldfish

Question
My fantail goldfish has started to flip upside down when it stops swimming is this normal or is this dangerous and could it die because of this

Answer
Dan , I am so sorry it took so long for me to get to you ....your goldie has a serious swimbladder infection and needs to be dosed with tetracycline now...take your carbon out of your filter and feed him a frozen pea cracked a week to stop this from happening again...don't forget to remove the shell later....Good Luck , Tina