I have a 50L tank, I want a external filter but most are up to 400L? Is it even worth me getting one? I mean I can easily pay the money for one and I believe it's much better for the fish.
Try the Marina S15. Slim, adjustable flow, great (I have the S10) underwater intake, silent, and has covered intake.
Or try the Marineland Penguin 100. Also a very good filter. I have the 150 model, has never had any problems ever.