Is the plural of goldfish, goldfi?

Inspired by Cymbeline's Goldfish for the New Year, I decided to give my daughter a goldfish to symbolise good luck in the form of tranquility, wisdom and long life.
Short of actually buying a fish, tank, food etc from the local garden centre, I couldn't find a goldfish anywhere.
We decided to make an easy origami goldfish instead, and had a good laugh whilst we were doing it. During our chat, we decided that the plural goldfishes, sounded clumsy, so we have invented our own plural goldfi!