How to remove imprint of a circle when moving it

[bigmanaw]

Been using Gimp for about a week now but cant seem to find an answer for this. Im trying to put three same size circles on a page but when i move them it always leaves a faint border behind and i cant seem to remove it. I float the image to allow me to move it and then anchor down so i assume im doing this bit right but the imprint is left behind. Picture attached.