Helping Selecting A Heater For Betta Tank

Hi ppl
Many of you will hav already seen my posts on which betta to get and also what tank but just once more i need your help. Im planning on getting this tank below it holds 3-4 gallons


Sorry I can remeber your name but you advised me that a 25watt heater would be suitable but im having real problems finding one
Does anyone know if a 50watt heater would be suitable?
Im planning on buying the tank tomorrow which takes 3-5days so really need to know quick as my betta can only be held for 3 days

I suppose i can manage a few days without one but any help you can give would be great
im in the uk
thanks

Have a lookie on here- http/www.aquatics-online.co.uk/Z039129.asp
Don't buy the cheapest, they aren't normally very good. I use Visitherm, but its up to you

https/sslrelay.com/rocketrading.co.uk/ses...ndex.shopscript

The Reef One 25 watt is on that page about £13 I think.