Purchased a 3" Silver Arowana last week. Within 5 minutes of releasing into aquarium, I offered frozen blood worms and he/she immediatiely accepted. Have had no problems to date. Currently at approx. 3.25-3.5 inches. Have read that the smaller aros are fragile and difficult to raise. What are the common problems and what indicators should I be on the look out for? Currentl keeping water level 3" below cover. Currenly have similar size goldfish, Synodontis ocellifer (cat) and black ghost knifefish is a 55 gallon tank with multiple filtration systems. Also, will a 240 gallon be sufficient long term for my current stock? Would I need a larger tank if I wanted to add a stingray (motoro or leopaldi)?