Hi bzbee!
I'm glad your gourami got better! I would be very cautious about using Melafix on a labyrinth fish. Although it is a wonderful treatment for other fish, the active ingredient seems to adversely affect the labyrinth organ. It's similar to us getting a noxious gas in our lungs. I have used Melafix on one of my bettas and he fell like a rock to the bottom of the tank. I immediately did a very large water change and he perked up. So, in my experience and opinion, I would not use Melafix on labyrinth fish. However, if you want to try it, be very watchful of any signs of stress in the gourami, do a water change every day before dosing for that day, and do another water change and run carbon at the end of treatment, if you treat in the main tank. Melafix doesn't harm the biological filter and it's not really necessary to use carbon to remove it, but with the gourami, I would make sure it's all gone. Good luck!