Sterlets

Hi , my first post here , just a quick question.

I have 2 sterlets in my pond , which are fine and healthy(apart from
one which insists on dragging half the pond round with his tail) , as
i have only had them for 6 month i have no idea how to treat them over
the winter months , pond shop people say treat them the same as rest
of my fish , does anyone own sterlets?...any advice would be
appreciated.

Many thanks

Amanda