Melafix's main ingredient is tea tree oil, which can be purchased on its own. There are formulas on the web and the forum on how to make your own. Search for "melafake" The biggest difference between Melafix and melafake is that Melafiz contains small amount of chelating chemicals -- chemicals that help keep the oil and water dissolved together. Otherwise, in melafix, the oil and water phases seperate. So, if you do make your own melafake, you have to shake it very vigorously before use -- you want the oil and water to be as mixed as possible.
Now, as to how well melafix/melafake works ... that is another question. I personally don't see a lot of improvement. I think that more frequent water changes will help just about anything Melafix helps. It is such a mild antobacterial that any real bacterial problems will most liekly need the bigger guns anyway. And I've seen the claims of spurring regrowth, but again, I think that water changes and higher protein diet helps that just as much. But some people swear by it, and if they have good results with it, that is great for them.