im alittle confused as to how much to feed. i put a pinch of food in and the bubbler and filter manage to stir it up good and my fish chase after it and after about 5 minutes they have finally finished chasing down all the particles and then they hang out at the top like they are waiting for more food..and when i do feed them(2-3 times a day) they are def. hungry..am i feeding them enough??