I had a duck abandon her egg at my front door. Right now we have a make shift incubator which includes a 10 gallon aquarium and a heater lamp. We've had the egg about a week now. It's rotated every 4 hours. Today I candled it the best I could however I've never raised a duck and all the pictures I've found say the egg is infertile but the yolk is getting bigger. Here's a picture any help?