set up 20 gallon tank saltwater tank, my first one so far, water getting to hot got a aquatic life 30" nice lighting and a vortech pump its nice to , water is at 79.5 degress need 78.0 , can i use a fan on top , or better chose a chiller to get it at a steady 78.0 also got a fluval e series heater for winter time , its not on yet, but if i get a chiller do i need the heater another question ? no fish yet just need it right before i put something live in tank