Deep cut in platies fin

[val]

I went to my tank this morning to check on the fish and feed them. I noticed one of my platies had a very deep slice in his back fin. It looks like a pizza slice was taken out. There's a chance the skin may have been cut, too. I think my crayfish tried to grab him during the night. His behavior is perfectly normal and he's eating just fine. How can I prevent this cut from getting fungus? But most of all, what do I do?

Valerie

 

[Dragonslair]

You need to remove him from your current tank and into a hospital tank, to which you should add a general tonic/antiseptic such as liqusil. To avoid more electrolyte loss(fluid) I suggest you add some stress coat or Melafix. Then you just need to leave it to God and mother nature.