melafix is one product used by different fish keepers with varying results. it helps in the regeneration, and healing of open wounds, cuts, burns and similar in fish. It DOES NOT dechlorinate water.
stress coat on the other hand is primarily a dechlorinator - but also helps in building up the slimy coating that fish have. its great to use on fish when they have scratches, cloudy eye, burns, cuts etc. I think its far better than any thing else on the market, and i personally use it too - and you cannot overdose on stress coat. its also the more holistic approach to solving fishy problems.
In a commercial environment, I use melafix and formalin in a hot water solution, and keep the shops fish nets in. that stops nasties from spreading from tank to tank, and with a lot of tanks nothing is worth taking the risk. plus melafix makes the fish area smell all nice lol.
HTH