aquarium treatment interactions

Question
We have a ten gallon tank that has been set up for about 1 and 1/2 years.  We have six tetras, a guppy, and a goldfish.  Earlier today we noticed our phantom tetra acting strange and his fins looked ragged around the edges.  I used an antifungal treatment, the active ingredients are malachite green and arciflavine hydrochloride.  When I checked on the fish this evening, the phantom tetra looked fat and bug-eyed, like he has dropsy.  My wife mentioned that she's seen some of the other shorter finned tetras nip at him before, so I'm beginning to wonder if the ragged fins are because of the other fish.  I also now need to know if it's safe to use an anti-bacterial treatment (the one I have has formalin and benzalkonium chloride as it's active ingredients) before the anti-fungal treatment is fully out of the tank.  They're both by the same company, Aquarium Products, but I couldn't get their website to load so I figured I'd ask an expert.
                          Thanks.

Answer
Hi James;

The other fish are picking on him because he is sick. It is a normal and natural reaction to eliminate weak or sick fish. The medications you mentioned aren't going to help him, I'm afraid.

He is suffering from dropsy, probably the result of some type of organ failure. Organ failure can be caused by infection, cancer, old age, genetic deformity, etc. Depending on the organ (kidneys, liver, heart) It will cause fluid build-up in his body. That's why his body is swelling. The only medication that might possibly help him is Maracyn 2. It is made by Mardel. It gets inside the fish to treat possible infection that caused the failure in the first place. By the time the poor fish is showing symptoms it is usually too late. It doesn't hurt to try though. Sometimes organs recover and begin working again once bacterial infection is treated.

If you have had him for a year and a half, he a "senior citizen" now. They are already several months old when we buy them and this would make him about 2 years.

It would be best to separate him to another tank if you can. The other fish are going to keep picking on him until he dies. He has a much better chance to recover (if it is possible) if he is alone. He could linger for several days like this with treatment or not. Even a small breeder net that hangs in the tank would be helpful. This way he could still benefit from the heater and filter in the original tank.

Hoping for the best and I wish I had more encouraging news for you.......

Followups welcome

At Your Service;
Chris Robbins