So now if you ask the same question to 50 betta breeders, you are likely to get 50 answers, not one of which exactly the same as the other. Confused? Join the club!! :). 

Although I have quite a few years with bettas under my belt, I do not claim to be an expert on everything and to know it all. Since we often don't know exactly what is wrong with a sick betta (because we never do get a bacterial analysis to know for sure which strain of what bacteria is present) we usually go "by feel". We use the spaghetti theory (a very sound scientific approach LOL), which states that if you throw enough spaghettis on a wall one of them will stick :). Over the years, (and many walls covered in pasta later LOL), you start developing your own recipes and opinions about certain medications, brands, etc...

Ok now that I have said that, you ask my opinion about Melafix. The interesting thing about this medication is that it is herbal. It is not an antibiotic or hard core chemical. Have I used it a lot in the past? No. I have had luck with my own recipes (which did not include Melafix) so I stuck to my second most scientific theory which states "If it is not broken, don't fix it!!". Have I ever used Melafix? Yes. Has it ever killed any of my fish? No (a good sign LOL). Does it make the water stink like eucalyptus? Yes! (but that is not unpleasant. If Melafix does not heal your fish, it will, at the very least, deodorize your apartment LOL.) Have I - or do I personally know people who have- ever mixed Melafix with other antibiotics? Yes. Did it kill the bettas? No (a good sign X2). Did the bettas heal? Some did, some didn't. Did the Melafix heal them or the antibiotic that was mixed with it? Who the heck knows LOL.

My final verdict: If your betta has fin rot it can be either fungal or bacterial. Super Sulfa (like its name indicates) is sulfas (great for fungus - not so effective for bacteria) so you are only hitting one of two possible culprits. What I would do is combine Spectrogram (has both kanacyn for bacterial - this is a broad spectrum antibiotic- and sulfas for fungus infections) with Melafix (if you do want to use Melafix). I have mixed Kanacyn and Melafix successfully in the past and with good results. I am not sure how effective Melafix really is but since it doesn't seem to hurt, why not add it in the mix anyways? I wouldn't add anything else in there cause your concoction might explode!!! LOL. Goodluck, and if you don't mind, do share your final results with me, for future data.