Miso Soup!

Last night, I tried to make a miso soup with daikon and tofu, but it didn't work. The fish broth that I used was salty, and so was the miso. I can't make the miso less salty so I guess the only solution is to try and find a low-salt fish broth. Admittedly I didn't look around, just two grocery stores, but I'm really fond of the Better Than Broth brand, and they don't make low-salt variants. They've been known to like restaurant-bought miso soups. Anyone have any good tips for making a miso even the kids will eat?