Wow, these fish are huge! And beautiful! If they grow any larger than that, you'll soon need a larger tank! I'm not saying yours is small, but these kinds of fish would probably love that 125G, wouldn't they!
The only reason why I say the tank is too small is because (maybe not now) but the pleco will get much much larger, and I assume so will the other fish.. I would definitely consider upgrading if you can
The Pacu, Pleco and the Arowanas will all get huge and an up grade to at least a 250G in the next year will probably be needed.
They are also huge waste producers so I assume your doing at least 50% water changes once or twice a week?