The endli will come around. I got mine to eat floating cichlid gold as a youngster. If you use massivore it might be a good idea to break it up, because I had a small poly choke on it and die.
long time ago when I ran out of feeders, and ran out of cash, lol, I gave my bichirs floating pellets, since we didn't have sinking pellets here. The sens would came up to the top, smelled the food and then they ignored it. But after a few days, they started eating them, then follows by my endlis, my ornates, and my laps, but they're all history now, since I sold them all,