So in my 70G i have 4x sens 3-6" and 2x Dels 4-5" and i call them the wolf pack cuz of how they search for food. but recently i started to feed them once a day and the food just dissapeared. i felt like i was under feeding them but most ppl say they feed them once a day. and noticed that my rainbow shark had been missing and just found what was left of the body under the del...how often should i feed these guys?