An Inside Edition investigation has found some restaurants are serving a cheaper fish than what's on the menu. A third of restaurants tested in Atlanta served up cheaper fish. We visited 22 restaurants in Tampa and Atlanta and ordered cod, grouper and catfish. Samples were sent to a lab for DNA testing. The results showed that all the Tampa restaurants served fish as it appeared on their menus, but out of the restaurants tested in Atlanta, one-third served a cheaper fish than advertised.