For now, don't go towards medication if you're worried about fin growth. I never go towards medication...for the most part, they are hardly necessary unless I'm dealing with something REAL nasty.
The first step is clean, clean water.
You have a choice of adding aquarium salt. If you do add aquarium salt, simply put in the recommended amount (the steps are very simply if you have some sort of measuring device). I definitely do not recommend more, however it's your choice if you decide to put in less. I don't, but it's still your own choice.