Hi Kay, Cecil has some good points.Your pump should be at least 1.5 CFM depending on your diffuser.Do you know what pump and diffuser you have as even a 7inch medium pore stone (not plugged) will keep an open area all winter(common on windmills) What depth is your pond and where do you have your diffuser placed? Also if you have a pressure guage on your system I can tell you if you are plugging.Figure 1/2 lb of air needed to push 1 ft of depth or a diffuser in 12 ft of water will usually show about 7 lb in the winter (cooler heavier water) I only run the systems in our display ponds to create clear ice and monitor the DO level and find my levels dont drop below 5-6 ppm in the evening which is when you will typically have a reduction.If I have clear ice for more than 2-3 weeks I will open up an area to allow for gass escape if the air temps are not below 20 degree F. I also believe that super cooling the pond bottom in not good as fish need a warm area 39 F to maintain health. The every 2-3 weeks is just a guess as I do not monitor those levels.In a pond your size we normally install a diffuser in a shallow area offset to the main diffuser to allow for winter mixing. If the pump is only 1-1.5 CFM then we run a seperate line with a manifold so we can run the shallow one in the winter and the main one in the spring summer and fall.If your diffuser area freezes up and your system will not reopen it something is wrong and you may not be getting the positive effects in the summer either. Hope this helps Ted
