Oscar fish is a hardy creature, and its survival rate is amazing. Oscar tank should have clean, warm water and plenty of space. They enjoy digging; thus, a sand-based aquarium with floating type of plants and rocks is highly appreciated. The minimum tank size should be 55-75 gallons. Being omnivorous, they are good with anything when it comes to food. Plants, small feeder fish, crustaceans, insects, worms, brine shrimp, fish pellets and snails.