I an thinking of getting another silver arowana. 2 years ago i had one that was 3-3.5inches but it died after 5 days. He was in a 55 gallon tank good filtration. An emporor 500 the temp was 75-77 his ph was 7.5-7.9. When he died he would flounce around the tank swim eratic he was doing good for the first 3 days eating he had know tank mates. Any idia why the died