Can I Use This Filter? :)

[annaw123]

I have a 100 litre tank, but my filter has always been a bit crappy, its one of those fluval U ones and isnt very reliable. So then i found in my cupboard an unused aqua flow 400, still all boxed and everything, but its for a 200 - 400L tank ....
to use or not to use? i know its best to use more filtration rather than less but i want some advice before trying this

Cheers guys!