Pond skating safety?

right next to my house, is a good sized pond, about the size of an olympic sized swimming pool, maybe a little bigger. Now, its completely frozen, and my family and I wanted to be able to skate on it, as well as some of the other neighbors on our street, theres about 10 other houses, since the pond isn't technically on our property it belongs to the street. How can i tell if its safe to skate? Considering its a man-made pond, it shouldn't be deeper than 5 feet, thats what Im guessing. It does have fish, turtles, crayfish, etc. And unfrozen, its typically an opaque green color. We all threw rocks across it, big and little, they all slipped to the other side of the pond, and heavy rocks (about 5 lbs) left a slight dent when dropped directly on the ice from hand height. There are a few cracks along the side, but I cant tell how thick the ice is. How can I make sure its safe? I can post pictures of the pond, if that helps.