They can grow up to 20 inches in an aquarium. They are nocturnal spending the day lying on the bottom on their sides as if they were dead. The water temperature should be between 72 and 80 degrees. Ph should be slightly acidic to neutral. They eat blackworms, bloodworms, and shrimp, either live or freeze dried. Make sure to feed them at night though or the tank mates will most likely eat the food before the Ossa Knife Fish even wake up.