Goldfish, betta and Melafix

Question
Help! I have an injured Betta that someone placed in the same container as another male... his fins and tail are in tatters...  I read on another experts answer that you can use Melafix to help heal fins but some people told me that it can actually kill your betta not help it... ?  I don't want to kill him, any suggestions for treatment?

Also, my goldfish just started acting weird.  I have had two for four years and have had only one problem with them... I just moved and in the last few months my goldfish has lost alot of his color and is now a white gold fish.  Today he began acting odd... swimming sideways, not keeping his balance, laying on the bottom, etc.  His fins are showing signs of hemorrhaging and looking a bit ragged.. so I separated him and added a little aquarium salt and water conditioner plus a few drops of melafix....
Any other suggestions?
Thank you for your time!
K

Answer
Kari,                                                        Melafix is derived from the oil of a tea tree. Therefore is a very natural cure. I think it would be a good medication to use , since it is not harsh. I think I would also stress coat. As for your goldie, he has a swim bladder infection. I would go get some tetracycline.....a good broad spectrum antibiotic. Use this for 7 days and don't forget to remove your carbon. After you have medicated the 7 days do a 25% water change and new filter. You can feed your goldies a frozen pea pionched between your fingers to release the meat once a weak to prevent this from happening again. Also You can get a veggie clip from your local petshop and cut orange slices kinda thin and take the rind of half, put it into the clip and stick it inside your tank. Your goldies will love your for it. It is great for vitamin C and color. Don't leave it in overnight. Good Luck, Tina