Harp and carp along wi' me

In the ponds in the garden we have fish. The small bottom pond has five golden orfe, which went in at about two inches long and have now grown to about nine inches. The top pond has regular goldfish; a big mummy fish and her babies (daddy fish died). Over the years the babies have mostly changed from black to gold, and most are about three inches long in comparison with their mum who's about six or seven inches. One of the baby fish, however, is very much bigger than the rest and is about the length of the mum and is now enormously fat. She (I'm assuming it's a she-fish who's full of spawn) seems to be expanding by the day and is beginning to resemble a startled puffer fish even down to the spiny appearance; she's so fat that all her scales stick out instead of lying flat. We've called her Mrs Creosote and are searching for the piscine equivalent of a leetle waffer-theen meent to offer.