There have been a lot of test done on knot strength and fluorocarbon. The fish n fool knot retains 100% of the lines strength with fluorocarbon. In some cases it will even make the line stronger than its rating! Google knot wars and watch all of the knots and lines tested, then check out tackletour.com and read up on their review of various fluorocarbons.
If anyone is breaking off fish they need to practice the art of fighting a fish instead of blaming the line. :lol: Your drag may be to tight, rod to still for the line test you are using. Anyone coming from regular mono will need to loosen the drag for fluorocarbon as it does not stretch as much.