it is a beautiful fish
That is NOT an Arowana. It is a Arapaima and it is a baby one at that.There are many aquarium fish that people impulse buy because they're cute, or they don't know how big they can actually get. Here's a list of some of those giants. Feel free to add to the list. Research before you buy!
-Arowana Osteoglossum bicirrhosum >4ft.
My lfs sells arowanas. Some are only 4", and we have some bigger ones nearly 2'. Even though the big ones are right next to the small ones, people assume theya re a completely different species and then get mad when they find out their cute little arro is now a foot long and ate all the fish in the tank.
By the way, here's a good pic of an oscar, the fish people most often buy that ends up growing out of their tank. I see kids walk out with a 10 gallon tank and a baby oscar in a bag. Poor oscars.
Really big fish, the arapaima-
IMO, pet shops shouldn't order these species at all. I'm opening a LFS soon, and won't even carry oscars except by demand, and oscars are small (relatively speaking). My problem with Astronatus is that too many live in 20 gallons until they die of hole-in-the-head or simply foul conditions. Every aspect of the pet hobby has these animals people aren't prepared to care for the course of their life, whether it's Burmese pythons, pot-bellied pigs, green iguanas, or pacu.These fish can grow to be larger than people realise and pet shops should advertise this when selling.
Most people haven't seen a 16 inch oscar, I'm guessing! They get MUCH bigger than most folks have laid eyes on. I've seen many breeder size fish that couldn't easily turn around in a 55 (12 inch wide tank). One oscar can live some two years in a 55, but it will get hole in the head, bacterial infections, lateral line disease, or worse without huge regular water changes. They might can live in a tank that size, but they "need" much, much larger.Why not oscars? They only need 55 gallons...there are many many more fish that grow to large...