"Please tell me what to do," the man says desperately. He obviously loves his goldfish.

"Please tell me what you've put in their water," the vet counters. From the tank's blue-ish, greenish, yellowish murkiness, she thinks she already knows, but she wants confirmation, which he gives her.

A week previously, he felt his goldfish needed some "refreshing". They weren't ill, just not as "bright" as they once were.

At his local fish shop, he bought some antibiotic powder. "I only put in a little bit," he tells the vet, "just half the packet."

The fish still weren't doing well. A few days later, he dumped in some methylene blue, and a bit later, some malachite green.

Each of these medications treats specific complaints, but together, they pack a wallop that very few animals could handle, even healthy ones.

Fish are not the only pets who can be over-medicated or mis-medicated. A reader has just e-mailed me about her German shepherd, who has been suffering from a "fungus" for the past four years.

"The medicine the vet gave me doesn't work!" she says, in obvious frustration.

Instead, she has consulted a friend, whose golden retriever also has bad skin problems. She has also headed for the Internet and discovered what appears to be an "advertorial" by a lady whose white shepherd had skin problems until she started using a certain medication. The advertorial comes with impressive "before" photos of a dog in a terrible state and "after" photos showing a happy, healthy animal.

"I'm going to get this medicine," my reader says. "Please tell me I'm on the right track."

Although I'm not a vet, I know that before you can treat a fungus, you must ascertain which fungus the dog has. To my knowledge, there is no universal treatment against all fungus infestations.

To identify the fungus, the vet must take skin samples and either send them off to a lab or do a culture in the clinic. Each fungus has a specific treatment, usually involving a particular medication, a medicated shampoo and lots of vitamins.

Some (but not all) fungi, like ringworm, release spores into the environment.

You can treat your animal all you want, but if you don't disinfect the bedding, floors and everywhere else, re-infection is certain.

Treatment is complex, especially if your dog is suffering from infestations of different fungi. In addition, recovery takes a long time - the lesions must heal, the skin recover and the fur grow back.

I advised the reader to consult another vet. Second opinions never hurt, but I hear she's taking her dog back to the first vet.

As for the goldfish, the vet tells the man to change the water completely and add a dash of sea salt. "What, no medication?" he asks.

"Not a drop," she says firmly. In his case, the fish need time to recover from too much love.

By Laurie Rosenthal