First of all, the turtles can mix with other animal fine. mine do. ive had them with the bluegills for 2 years and theres not been a problem.
your turtles are with bluegill... semi large, fairly aggressive fish that live with turtles in the wild and know that turtles are dangerous. most fish will quickly be eaten by turtles.
Second of all, do you really think that a lightbulb is going to heat up 100gallons of water??!!!
yes. enough light output can warm up bulbs and due to heat transfer, warm up the water. many saltwater tanks need cooling fans because the lights warm up the water too much.
Bluegills do not need colder water anyways. they need a range of 67-75 and my water is 72 degrees.
ive seen A LOT of people with Oscars mixed in with turtles. So just think beforee you say something. i've been planning this all out for at least a year. anyways, if you didnt read my earlier post, i said i wont be getting the Oscar or the Adonis Catfish