Oswald (betta fish)

Question
Hello,
This is Juliette again (I'm the one who asked a question about whether or not my betta had fin rot and what I should do in general to keep him happy), and I have done every thing you have recommended for Oswald--the 5 gallon tank, varied diet,  and I am raising the temperature slowly to 80 degrees--but now I need to treat him. When I went to my pet store to get everything I needed, I asked if they sold Teracycline, but they didn't. They told me that melafix was the same thing as Teracycline, so I bought that. But today I read one of your answers to someone else's question and it said that you did not recommend Melafix and that it could kill the betta. If I stop treating him with melafix (I started yesterday), will I have time to order Teracycline online before the fin rot gets too severe? Is it even possible to switch from one medication to another or can that harm my fish?
I can't evaluate how bad his fin rot is, but he is a halfmoon betta and his fins/tail don't form a half-moon anymore, and his top fin is hanging on the side.

PS: I bought a filter with the tank. Does the current stress bettas or is it fine of there's a slight current because of the filter?

I'm so sorry I'm asking so many questions!
Juliette

Answer
Hi Juliette,
I can understand how devastating this can be when we cannot find the right medication.  
Do a complete water change to remove all of the melafix.  Melafix is extremely dangerous for bettas.  They can make his situation much worse, and kill him.  Melafix, is the same as Bettafix, only much higher concentration.  If you do use it, and I wouldn't recommend it, be very careful, and do only half dosages.
Does your pet store have Maracyn, and Maracyn-two?  If they do, combined these two medications, and treat your betta with this.  You would have to do a complete water change before treating him with another medication.  Melafix does not mix with Maracyn, and Maracyn-two, or Tetracycline.
I would also add Coppersafe.  This medication could be added with Maracyn, and Maracyn-two.  It is a very good medication against many diseases, such as parasites, and flukes.  When a fish has fungus, or fin, and tail rot, he is weak, and can easily be attacked by parasites.  Coppersafe helps eliminate parasites that could be eating away at your fish, or in the water.  There is no danger in adding coppersafe to Maracyn, and Maracyn-two.  
I hope you find these medications.  
Do not leave him in a full dose of Melafix.  Change all the water again if he is in a full dose, and dose him with half until you get the right medication.  Once you do have the right medication, do a complete water change, and let him rest a day from the Melafix treatment, then treat him with an antibiotic.  I have the same problem getting antibiotics where I live, so must buy them from the vet.
A slight current does not stress a betta.  They do prefer still water, but a little current will not bother him as long as he has no problem getting air at the surface.
I hope this helps
Lynda