What Heater For 25L Tank?

[APacman]

I've been doing some reading and it seems a 25W heater is about right, opinions?

Also does anyone suggest a particular brand of heaters they can really rely on? I've gone through two rubbish ones so willing to pay more if it'll work.
For such a small tank is it better or unnecessary to have a self regulating heater?

This might be urgent, can't be sure but I think my current heater is on it's last legs

 

[Cazgar]

Any 25w heater should do the job, but get one that the temp is adjustable.
The preset ones I've found to be unreliable

 

[Essjay]

I have 2 25 litre tanks. One has a 25w visitherm heater, the other has a 25w sera heater. Both work fine, and are also short enough to fit.