#16440 NO HEAT! (optional immersion heater and self regulating heat cable available) *200 head capacity. The water is completely surrounded by fully insulated polyethylene plastic - even the floats are insulated. In summer, the water is cooler and covered water protects against mosquitoes breeding, lowering the risk of spreading West Nile Virus. The covered water also keeps the water cooler and prevent water evaporation during dry months.