Your main considerations: When buying a portable immersion heater for troughs or buckets, safety is your overriding concern. Size is also important; get the correct wattage for the volume of water you’re looking to keep warm.
Sorting through the options:
• Heaters for large tanks, which typically run between 1,000 and 1,500 watts, are available in sinking or floating varieties.
• Smaller heaters, suitable for warming a single bucket of water, run between 250 and 1,000 watts. Both types of heaters have similar features.
• Look for models that shut off automatically when the desired temperature is reached, when the water level is low or when they are removed from the water. You’ll also want to see heavy plastic or aluminum casing around cords and a mechanism for keeping the heating element from coming into contact with the trough or bucket itself.
Cost: Single bucket heaters sell for roughly $40, large tough heaters can cost upward of $200.