Family: Auchenipteridae or Doradidae Range: South America Size: Up to 8 inches Diet: Omnivore Tank Set-up: Freshwater: Plants, rocks, driftwood Tank Conditions: 70-78ºF; pH 5.8-6.5; dH 4-7 Minimum Tank Capacity: 50 gallons Light: Medium Temperament: Peaceful Swimming Level: Bottom Care Level: Easy Reproduction: Egg Layer
Planetcatfish has some info on them http://www.planetcatfish.com/scripts/clog_link.php?q=liosomadoras+oncinus. My personal experience is they're easy to take care of hard to get feeding. Mine eat bloodworms,blackworms and earthworms. Though they're real secretive and you'll virtually never see them they're always hiding when the lights are on only comin out after they go off. They need a place to hide or they'll go buck lookin for one. You can use driftwood though I'd worry cause they lock their pectoral fins in and sometimes get stuck. I use rocks this way they can't get stuck, if you use floating plants they may be coaxed out during feedings during the day. Though at first I'd suggest feeding them with the lights out until they become used to the new tank. They should be fine with those tankmates they're pretty tough skinned so they've got some protection even if tankmates are semi-aggressive. Good luck and I hope this helps you.
Most growing oscars see anything smaller than themselves as food (IME). If the oscar gets the cat in it's mouth, the cat is going to lock it's fins (like klotsix described), and you will end up with two dead fish. If you mix the two, there is a good chance that you will find your O speared through the face from the inside. I'm just saying, it is something to think about.