1. Pet market: There are many pet markets in Xi 'an. You can go to the local pet market and look for stalls selling pet food. Generally, there are shops selling pet fish food. You can find small fish suitable for turtles in these shops.

2. Pet shops: In addition to the pet market, Xi 'an also has some pet shops that specialize in selling all kinds of pet supplies and food. You can go to these pet shops and ask if there are any small fish for turtles to eat.