Best Heater For A 17L Tank?

[coldcazzie]

Not my tank, for a friend. Have persuaded her not to put 2 goldfish in it, and to opt for a betta and 2 amano shrimp instead. Also giving her media from my filter, but no heater came with the tank so she needs to know which one to buy. The 17w should be fine... right?

 

[soybean]

I have a 25w in my 17l, 17w should be fine.

 

[BigbruiserAl]

I have a 20L and with the light on for 6 hrs the temp sits 24-26c all day with no heater in it.

 

[coldcazzie]

ah, it doesn't have a light on it...