I've had great luck with a 1000 watt stainless steel aquarium heater I bought from Amazon.com for about $100.00 for my 500 gallon systems. If your system is smaller you can get by with less watts.
Can this be mounted in an all plastic/poly tank?
Yes, just hang it on the side (inside) and you'll have no problems. One of my tanks is plastic and I've also hung it on the inside of my plastic stock tank that holds the RBC with no problem. No melting or damage.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.
