What you REALLY need for a NICE, easy to keep clean OSCAR tank:
A POWERFULL, I mean POWERFULL filter. And if you REALLY want to be LAZY get TWO. I think the perfect combination is a Powerhouse like the Aquaclear 500 that does 500Gallons PER HOUR and the Magnum 350 Deluxe! Yea this AquaClear500 tank will filter through it 500 gallons in one hour. (For a 50 gallon tank this means it filters ALL the water 10 TIMES in one hour!) Now use the AquaClear500 along with the MAGNUM 350 using the "MICROn-Filter" doing 100% filtration, NO BYPASS, and does it at 350 Gallons per water! Why BOTH? Well the Magnum 350 has this REALLY cool SPECIAL filter cartridge that filters out VERY VERY VERY tiny stuff which other filters CAN NOT catch. I personally had to use the Magnum 350 special FilterMedia to filter out some bad algae I had, I couldn't get rid of it ANY other way, chemicals didn't work, large water changes DID NOT work, nothing worked, yea the algae were like Microscopic but were SO DENSE you couldn't see 3inches deep into the water!!!(was a grass-green color) Using both filters will keep your water CRYSTAL CLEAR. The Magnum is a bit more expensive but is really worth it if you want a beautifull looking clear water tank free of even the smallest particles that would make your tank look "cloudy".
You might want to buy the AquaClear 500 First, it is cheaper. Only around $65 from the leading on-line pet stores. BUY-IT-FROM this major online pet store through this LINK. Here's more INFO on the AquaClear 500. and more info on the Magnum 350 Deluxe.
ALSO, the MAGNUM 350 will take a little bit more TIME than the Aquaclear to setup. If you buy it and need help just ask me and I will help you out, just POST on the BBS (Bulletin Board System) here's the LINK to it.
AND I figured I need not mention you really should have AT LEAST a 50gallon tank for 2 oscars. This is bare MINIMUM. Besides with these two filters you'll have a nice 100gallon or Bigger sparkling CLEAN! :)