The lawsuit filed by Goldwater Institute on Monday says the Arizona Board of Cosmetology overstepped its bounds when it decided the fish perform pedicures and are subject to regulatory control.
Cindy Vong opened Spa Fish Therapy in Gilbert last year and charged customers $30 to plunge their feet into a clean tank filled with fish, which nibble on customers' feet, removing dead skin.
The therapy is popular in Asia and some U.S. states. It uses small fish imported from China.
The board ordered the spa to close because the fish cannot be sterilized. Vong says the move cost her a substantial financial investment and lost business.