What is the best heater for a 29 Gallon tank

[sandmaan]

My tank is a 29 gallon tank and I need to buy a heater for that but I don't know what is the best wattage and the length of the heater also want to what would be the type with a regulator or without a regulator.

Please help me out my fish actually dieing due to the coldness of the water.

 

[BillD]

How cold is it? What type of fish? It is hard to imagine needing a heater in Sri Lanka. A 100 watt heater should be more than sufficient unless temps are dropping below 18 C.

 

[sandmaan]

Ahhhhhhhhhhhh.......... some one who knows about Sri Lanka. Well it's very cold and I think it's going down below 18c 'cos my tank is out side of the house and the fish is barbs (Tigers, Green, Albino).