One of the reasons why I love the Oase thermo canister filters is they have a 100-300W heater built in.
For most tropical freshwater fish, a heater is very important. The vast majority are looking for a temperature around 76 F. Unless you can keep the room that houses your tank at a minimum of 72 year round, your going to need a submersible heater. One of the reasons why I love the Oase thermo canister filters is they have a 100-300W heater built in. This allows you to keep you aquascape free of this additional component. For tanks 10 to 30 gallons I like to use a 100W heater, tanks 30-55 gallons I use a 200W and tanks above 55 gallons get a 300W.