Question for you all. I have a tank that's almost five months old. I have 12 fish. 8 septa tetras and 4 white skirt tetras. Two months ago I got a RedTail Shark a two weeks later it died. The local fish store replaced it. The new one recently died. It was a month old. I would feed it flakes and that's all. My water levels are great. No ammonia. Nitrates and Nitrites are zero. PH is 7.0. My goal is to have a healthy Red Tail Shark. Any suggestions? I was think maybe different food for them. My substrates in my tank are snow colored rocks. So light colored rocks. Would that be the reason why they keep dying as well. Love to hear any suggestions.