Question
Hello, My goldfish have been coming to the top of the pond.  I have had my pond for 5 years and they have never done that.  I live in Ohio and use a pond heater to keep an area of the pond open. The weather has been up and down this year, alternately freezing and unfreezing the pond.  The pond is 4 feet deep and I have never lost any fish over the winter.  The heater failed to keep the pond open for a day or two before I noticed it.  One of my fish has died and the rest are coming to the top of the pond even though there is an opening in the ice.  I know you're not supposed to feed fish in the winter and there is a hold to release the gases.  Any ideas?  Thank you,  Pt

Answer
They may have suffered while the pond was completely iced over.  Either the oxygen was too low or the toxic gases (carbon dioxide, methane, and hydrogen sulfide) were too high (trapped under the water).  How much ice is on the pond now?  Do you have any water movement still going?  I leave my waterfall going but many people don't.  If the only thing you have is the de-icer, I suggest adding an air stone to the pond.  Aeration is very important.  A hole in the ice may not be enough because it's a small area for gas exchange, and the water is not moving (unless your system is on like mine).

See my winterizing page at http://www.fishpondinfo.com/winter.htm for some links to aeration systems.  I use a Luft pump in my 153 gallon pond for aeration in the cold months.

Another note:  pond fish will come to the surface in the winter for no particular reason and not just because of low oxygen or toxic gases.  Since you mentioned that the pond was frozen over and has had fluctuating temperatures, I do think the problem is probably gas related.

Good luck!