My fish has a bad case of fin rot, I dont understand how he got it. I change his water once every week. I am using maradel maracyn and also bettafix plus to treat his water right now. I've been using the maracyn for 1 day and I am now on my second day now. The maracyn inst. were kind of confusing, dont really know how much to add to a 1/2 gal betta bowl, so I added a teaspoon. Should I change his water on the 2nd day as well. I'm so confused, can someone please help me.