In this case, diet is what a goldfish eats, not to loose weight.
Here's a little blurb I found about Probalance made by Penn Plax:
Penn Plax Pro Balance Goldfish Flake food is a total diet providing the
nutritional requirements formulated specifically for goldfish and other
cold water fish. Astaxathin is added to enhance the bold goldfish color.
Krill is added the appetite and digestibility. Goldfish Flake food contains
Amino Acid Additives, Stabilized Vitamin C which also promote healthy
growth and stimulate the appetitite of your fish,as well as vitamins A, D3
and E. E-Z Measure Cap for feeding measurements and prevention of overfeeding. Will not cloud the water. Feed 1-3 times daily as much as
your fish will eat in a 3 minute period. Size: 1 oz. container
Here's the link I got the info from:
http://www.petluvers.com/product4160.html