I have kept arowanas in the past. I can help you get your tank set up and give pretty accurate advice about care and husbandry of those fish.
Reds are not legal in the states, doesn't mean that they don't make it here.
Silver are the most common followed by the Jardini(gold) and the blacks. They are pretty much exclusively top-water swimmers and are great jumpers(a strong and weighted glass top or other type of inclosed canopy is a must). They come from the amazon, so they like soft, warm water. They show the best coloration, and look the nicest when you maintain discus-like water quality. They are far more forgiving than discus, and can handle excess waste, but you will see signs that they are not happy. I used to keep my pH around 6.4 and kept the temp around 80-82F.
As far as the set up... you will basically need to get rid of all of the rock and sand. What are you currently using for bio-media? I would rinse everything in fresh water except the bio-media. A lot of the bacteria will adapt to the freshwater environment. This doesn't mean that your tank is cycled, this just means you have a SMALL head start. I wouldn't start the tank with the arowana, give it a month(minimal time) before you introduce a fish like that. Buy a bottle of stability and a bottle of microbacter-7. Dump the entire bottle of microbacter-7 into the tank after you have filled and dechlorinated your newly filled tank. I have been using tap water for freshwater for a very very long time. Throw some prime in there and you are good to go. For the stability, add one cap for every 10 gallons every day until you run out. After 3 days of the stability, you should be able to add a few fish..... GOOD LUCK!
