Hello! As some of you may have heard I had plans to do a monster 500g. But due to $ I would be able to cut the price down in half by going with a 325. For the 500g I was going to go with some discus, an unkown kind of stingray and possibly an arowana. But I'm worried about size. Would I have to sacrifice the arowana in the downside? And as far as living I would want the silver to be able to live their whole life in that tank. The dimensions are 120x30x24. Thanks!