I use an airstone driven by a tetra luft pump to keep a hole open in the
ice on my 16' x 20' pond. It seems to work very well at preventing
winterkill and also accellarates the process of melting the ice when the
weather is warmer - I suppose because the small patch of open water
reduces albedo and allows the pond to absorb more solar energy than it
would otherwise.
A precautionary note- use a plastic pop bottle as a float to keep the
airstone suspended in the water column about 3 to 6 inches from the
surface. If the stone is placed in deep water it will turn the whole
pond over and there is a risk of freezing it the whole way down because
of the heat loss.
Also the pump itself needs to be protected from moisture. Either keep
the pump in the basement and run a line outside or build a shelter to
keep the pump dry. Also exercise caution with the extension cords used
to run the pump. Electricity and water can be a dangerous combination.
Jeff
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