freezing pond water

Question
My garden pond is 15' x 30' and has three levels in depth.  It starts at about 1', second section within the pond is about 1.5' and the main section is almost 2'.  I am able to add more water if necessary.  I need to know if there is an air temperature ratio to ice thickness.  I am a first year pond owner and want to give the fish enough room under the ice to survive the winter.  I live in Northeastern PA and winters can get as cold as zero to 10 below.

Answer
Hi Jean:  Colder water holds more oxygen then warmer water and in winter... the fish slow down so much that they do not use much oxygen.  A de-icer will keep the surface of the pond from freezing over as will a rapid current that breaks the waters surface.  I am a bit concerned that the pond may freeze entirely... You may want to consider a small shelter for the pond that would keep add some warmth but can be taken down in the spring... dave