Decided to put the 600 gallon into effect for the winter and hopefully keep the birds happier and healthier looking. I purchased a 1500 watt heater for the pool and hooked it up to a time. (I mean its 1500 freakin' watts, right??? I want to be able to pay my electricity bill) We are getting icing over the top of the pool in the morning. I break it with a shovel, but its not what I had invisioned! I'm an invisioner of pretty pen, pretty pool, and happy pretty duckies! Anyone know how many watts needed for 600 gallon tank. Cant find anything online. Thanks so much!