So my new betta fish seems to be a very picky eater. I've tried feeding him Top Fin pellets, Top Fin freeze-dried blood worms, and HBH flakes. He sucks them all up in his mouth but spits them back out. I've tried pre-soaking the food, but he doesn't seem to care. Is he just being stubborn? I've heard that it may take a couple days for the betta to get used to its new diet.