give your ascars a wider variety of food too if you decide to keep them. Oscars will eat a lot and will grow quickly which is why I agree with everyone else here that you need at least a 50 gallon for just those 2 oscars. Being dirty fish, you would also want a large filter with good circulation, probably a canister filter rated for 75 gallon tanks or more. Frozen food are great, I would mix it up more with brine shrimp, beefheart, spirulina, algea, spinach, etc. MOst frozen foods you find will be suitable but a common problem with oscars is malnutrition because they don't get a varied diet or enough food. Try to aoid live feeder fish for a loooong time. Many people want to feed feeder fish as soon as they can and that can lead to infections later on or malnutrition as they oscars sometimes stop eating anything else besides goldfish. Get a good pellet food too, that should be his main diet since it is well-rounded and fortified. I feed mine chopped peas too to help bring out color, aid in digestion and provide vegetable matter.