At this stage, they're somewhat sensitive to water quality. The bigger they get, the hardier they become.
Keep a tight, weighted lid on them at all times; do no under estimate their strength.
Mine was very stubborn when it came to changing up his diet, but that doesn't hold true to most. A well rounded meaty diet is good. Once they start hitting the 16" range or so though (about a year old) start limiting the meat and feeding more pellets, with meat as an occasional staple.
Be careful what you keep with them, because I've found from experience that they become very aggressive during the changing of seasons (fall and spring). Mine beat the hell out of my 14" Oscar to the point that I had to keep him in an outdoor pond over the summer in fear of the Arowana killing him.
Keep in mind at all times that they are extremely skittish fish, and do not do anything at all that could scare them. Once they get bigger, it's very common for them to seriously hurt themselves from trying to get away or jumping, simply because someone decided to do jumping jacks in the same room as the tank.
Just a few things that I have learned over the years that research isn't going to tell you.
Treat these beasts well and they'll prove to be some of the best fish you'll ever keep. Good luck
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