Tisty how does your loop run, seems a bit overly complicated from the picture. Wouldn't of been easier to go res => pump => gpu => rad(s) => res ? Like this:
In terms of fans, generally speaking you need fans on the radiators used. It all depends on what you want from your pc. Passive cooling is possible for leaving PC's on overnight if downloading but as soon you start loading cpu or gpu fans have to be used, albeit low rpm, as you will never really get enough heat disapation without them.
As for just pc case fans with watercooling, usualy good to have some to get some fair flow through the case. Mine now runs 200mm fan front and side, 120mm at rear and 2 120mm on rad in top of case. I want to remove the side 200 though for a full window but at the moment 200mm fans run at 500rpm and the 120mm are running at 900rpm. While still means fans I never have to change the speed of them whether idle or gaming to suits me, unfortunately the loudest in my case now is my pump which I am trying to make quiter.
@ LogitekG25: google is your friend but yes they can leak and yes they can destroy the whole pc but that is why you pick the right blocks, tubing and fittings to reduce risk of it and also leak test at the beginning to make sure there are no leaks when it comes to power up properly.