It will take a few days for your aro to adjust. How new is the tank? Did you properly cycle it, Arowanas do not do well with ammonia, so test your water daily if the tank is in fact new, and do water changes accordingly.
The clown loaches grow slow and will be fine in the 60g tank for a few years. However your 6" silver aro is gonna be 18-20" long with in a year, they grow incredibly fast. Unless you are going to be able to provide a tank that is at least 180g (6' x 2' x 2') in the next 6 months, I urge you to consider taking this fish back to the LFS.
BTW the 180g tank I mention before will still not even be big enough to keep the aro in once it gets 26 plus inches.