if your talking about the end that hooks into the fx-5, did you put the circular steel hose clamp on it? I've never had any problems, but if the tubing itself is leaking, because of a hole it isn't too expensive to just go buy new ones.
ok, maybe my pic will better explain the problem. the fx5 is connected directly to the inlet & output pvc connector. the leak happened @ the out of the output tube where it connects to the pvc piping. i had no problem w/it for over a yr. however it was set up for my smaller tank which both tubes were inside the tank, so even if there were leaks, it didn't matter.
in the first pic, the horizontal pipe w/a ball valve is the inlet pipe, and the vertical pipe w/a check valve is the return. the leak happened to the rubber nozzle at this end of the tubing