Many times painteds will "winter over"- stay in ground until Spring if late Summer weather is not optimal for hatching. It may take a week or so, or less, for them to eat- depends on how much egg sack was digested over winter. Koi pond is a bad idea till the little guys are well started.I've kept mine in a small aquarium and fed chopped minnows, worms, and pelleted food till they were big enough to release.Daily H2O cleaning is a must, so keep the tank simple. Good Luck!