What is the difference between Flubendazole and Fenbendazole ?

[Guppysnail]

I’ve used Fenbendazole for different worm and parasite issues. I often hear Flubendazole mentioned but have not used it. 
 

I know they are both benzimidazoles and anthelmintic. But are they interchangeable?

If not interchangeable what do each treat in fish and where do they overlap on what they treat in fish? 
 

Is one harder on fish than the other? 
 

@Colu @Odd Duck

 

[Fish Folk]

FLU-B: https://en.wikipedia.org/wiki/Flubendazole

FEN-B: https://en.wikipedia.org/wiki/Fenbendazole

[Odd Duck]

They are very nearly interchangeable in their actions. Sometimes one will be more effective than the other or vice versa, but with appropriate dosing I would consider them essentially interchangeable until proven otherwise on a specific case.