got a orange cap oranda medium size and she floats after she eats the flakes .I tried swiching the food to pebbles . she is ok after a few hours .i gave her a pee nothing she floats to the top of the tank . i changed the tank  and gave her less food but she pigs out . i feel so bad for because she floats all day. i pray that she will stop floating but she stops floating after she digest her food

Orandas are especially prone to problems in the digestive tract, so if you notice that it's floating about in the tank, you should definitely consider feeding a more varied diet. Mainly focusing on veggies or live foods to supplement the staple flakes or pellets!
A very easy to get live food would be blood worms, they're sold in frozen form, freeze-dried or packed in gel. They're very nutritious and the fish love them! Other foods you might want to try as frozen or freeze-dried would be tubifex worms, brine shrimp, daphnia, krill or mosquito larvae. (You can catch the mosquito larvae yourself in a small bucket of water)
You should also be feeding vegetables quite regularly, like peas! But not just one a day or something like that, feed them peas many times a week! Peas work wonders on clearing out the digestive system on goldfish. You could also try sliced cucumber, lettuce, zucchini, boiled carrot... try anything that doesn't contain spices (or spinach) and see what your fish likes more. Fruit is alright too, but can be more messy than veggies due to fruit juices, so you could feed some banana, orange or water melon before water changes
And finally, to make the staple food easier to digest, you could soak the pellets for a while so they'll be easier to eat!

Then you should follow the advice of previous poster, don't feed the fish for a few days, and then feed peas until it clears up. Make sure that your water quality is good as well! Test the pH, ammonia, nitrite and nitrate.