Most of the fish in the Philippines are brackish water fish. Most that can tolerate fully freshwater are mostly gobiidae and usually stay small. Not really an ideal tank mates for an arowana as they might end up as food.
We do have a nice looking fish that can tolerate fully fresh water called Tiger Bass or Targetfish (Terapon jarbua). It's a type of grunter that can be found in estuaries. I did caught some before when they were stranded in the river that close to the sea. Placed them in my pond with aros. They looked cool with silver-white body with horizontal stripes. Almost zebra like. I also had a marble goby (Oxyeleotris marmorata) which I also mix with aros before. I mixed swamp eels (Monopterus albus) before too with aros. Some a little bit risky as when they go hungry they like to bite whatever that passed by. They are also known as tulip eel as when they ambush for food the head stands up right looking like a tulip plant. Also there are many Indo-pacific tarpons (Megalops cyprinoides) being sold as feeders but can look good with aros as tankmates as they can also tolerate fully freshwater. I also caught some nice looking freshwater snappers (Lutjanus fuscescens) but never really did mixed them with aros as they end up on the dinner table.
As for Asian Arowanas.... Asian aros are very popular in the Philippines just like any other Asian countries. However getting asian aros in the Philippines is not really the best thing to do as the price is much more expensive than here in Canada. Also you will see plenty of green or banjar labeled as SR or XB. Not the best place to get asian aros unless you go to some of the private dealers.
Anyone that goes to the Philippines that is into the fish hobby must visit Cartimar. It's a chain of pet store where you will find fresh water and salt water fish. You can get some cheaper aquarium equipment as well. However most of the stocks are goldfish, kois and other common fish you will find in many of the LFS here in Canada. However there are some nice fish that will pop out from time to time. I've always wanted to get some of the freshwater shrimps that are easily breed and are good for feeders as they get to 4-6".