It was a busy downtown Tucson Saturday night, and we were dining at Barrio, one of downtown's top haunts. After perusing the delicious (if rarely changing) menu, one dish caught our eye: the fish tacos. We asked what the fish of the day was, and we were chagrinned to hear salmon. No, no, no; salmon is great, but not in fish tacos, not served with black beans, habanero tomatillo salsa, guacamole and grilled pineapple salsa. We begged for an alternative, and after checking in with the cook, our server returned with fantastic news: Tilapia was available. And that's how we came about the best fish tacos we've ever had the opportunity to eat.