is your aquarium wide enough?what arowana do u have and how big?
okay do you want something to clean up your aquarium (wast,un eaten food etc)
or something to look at for hours?
if you want something to clean your aquarium then I would buy a small skl of hoplo catfish,they grow up to 7" and they are pretty much cheap and also they are very hard fish but if you want something to look at go with ray but ray are hard to keep.