Damn! (some) guys here need to chill out and explain some things a little more lightly.
I'll agree mostly with what was said above (perhaps slightly more politely than some). No aro is a good starter in a 55 unless you already have a bigger tank. They grow fast----some up to 2" per month.
If you like the way an arowana looks and dont have the space or funds for a large tank you should look into an african butterfly fish.
That said, a 6" silver or jardini would probably be your best bet. Be sure to do your homework though, they are unlike any other fish and each type has different requirements
I'll agree mostly with what was said above (perhaps slightly more politely than some). No aro is a good starter in a 55 unless you already have a bigger tank. They grow fast----some up to 2" per month.
If you like the way an arowana looks and dont have the space or funds for a large tank you should look into an african butterfly fish.
That said, a 6" silver or jardini would probably be your best bet. Be sure to do your homework though, they are unlike any other fish and each type has different requirements