good and insensitive to cold

I purposely my two pond pumps over winter in the basin, 40cm deep left. now where is finally frost-free, at 12.4., I degenerates least a trial and both pumps are started immediately and worked normally. The basin is 40cm deep and the pump were the beginning of the winter full in the water today, not much water was in the tank, that is, the pumps were free of water basins, Gee, only Oasis pumps, delivery head more than necessary and promised, these are great products, a little more money but makes itself paid