I've rarely had them take anything but frozen foods. When I first got a pair of them, they ate flake food a few times, but other than that they refused it altogether. Frozen brine, worms or nightcrawlers (chopped and rinsed), small frozen bloodworms, frozen mysis, blackworms, etc. were all taken.
And yes, the brackish/freshwater thing about BB's is in debate. What most people don't get is that there aren't just one type, but many different variants. Some like somewhat different water conditions then others- while one likes soft water, another likes high end brackish water etc. While most people keep them in freshwater, it's best to start them in low end brackish to begin with. Most come from areas that switch salinity levels quite readily throughout the day, so a really low sg level may be of benefit.
Good luck with them! I think I may start up a ten gallon in a few weeks for a few pairs of them, hopefully this time they'll go all the way and breed.