Some great food for flower horns is Pearl flowerhorn feed. Also feeding them live food at least a several times a week will keep its color. Natural sunlight is awesome but if you cant give it that then you can bring out the red color with a coralife trichromatic light or using a blue light to bring out the nice blues. Another secret is if you keep the lights on longer than 10 hours a day it will make your fish grow and get great color. And one more thing I know is that if you keep another flower horn in the same tank but keep them seperated than they will get a deep deep red eye. Hope this information will help you a little. fred