What is my fish sick with?

[George9]

Yesterday I noticed a piece missing from my dwarf gouramis bottom fin (not sure what its called, Its the fin on the underside of him.) Around the tear, its brownish. I do 15% water changes three times a week. The tank size is 20 gallons. Could this be some sort of fin rot?Or did one of my other fish take a piece out of him, I have two tiger barbs and a molly. I haven't had any problems before with any of them picking on each other.

He's acting normal and eating normally.

 

[librarygirl]

Sorry about your fish. I don't have enough experience to answer this but I hope someone else helps you. Good luck.

 

[George9]

Im pretty sure it's fin Rot based on other answers on other posts. I'm treating him now.

 

[zfarrias1]

definitely fin rot, you might want to also do 25% WCs instead of 15%

 

[George9]

That's what I've been doing. How often should I do them? I'm treating him with Melafix now, on the third day