Emergency Treatment

The best point at which to treat guppy diseases is when they first show signs of stress. Ammonia poisoning is usually indicated by the sudden death of one or two guppies that show no signs of obvious disease. Guppies that stop eating and hang in a group at the back of the tank, either at the top or bottom is another sign of stress.

Although some diseases are extremely contagious and can attack healthy guppies even in well-maintained tanks, the vast majority of diseased guppies are the result of stress. The most common cause of guppy stress is poor water conditions or a sudden change in tank water parameters (such as pH bounce). Once disease is firmly established in a tank it is usually impossible to stop.

1. If one or more of your fish become diseased, check the chemistry of the water, including heavy metals, ammonia and nitrite levels. Remove diseased fish. Resist the natural impulse to feed sick fish, as uneaten food quickly adds toxins to the water. If the water tests zero for heavy metals, ammonia and nitrite then it’s usually a pathogen.
2. Make an immediate 75% water change and then next day 50% water changes to bring down the level of bacteria or toxins in the water. Doing larger water changes will stress the fish unless the new water has the exact same temperature, pH and hardness of the water that is being replaced.
3. Do not resort to medications for a quick fix. Most bacterial or virus medications disturb the biological cycle, creating stressful conditions just when the fish are least able to tolerate it. Medications formulated to kill internal parasites and some external parasites, as well as fungi and bacteria, have a higher success rate. It is very important to follow recommended dosage levels and treatment programs. Overdosing will stress or kill the fish. Under dosing ensures the survival of medication-resistant pathogens.
4. If your fish do not recover within the first day or so, I usually recommend culling the tank. If you cannot do that, and you have no idea what pathogen is affecting your fish, use Potassium Permanganate to kill most external pathogens (except such large parasites as lernea and very small bacterial or fungal diseases). PP also reduces the organic load in the tank, creating more favorable conditions for recovery. It is a chemical found in many pet store "water clarifier" products. You might want to order some now and keep it on hand.
5. Diseased store bought fish are common. Very few fish stores have the knowledge or desire to maintain proper water conditions for guppies, and the guppies they buy wholesale often arrive at the store severely stressed. Disease may take several days or weeks to appear. Even guppies acquired from friends or a dealer may have diseases your fish are not immune to. An isolation tank is imperative.
6. Put newly introduced fish through my recommend "3 Step Treatment" program to screen them against the most common diseases. This is a practice used at large aquariums to ensure new fish do not introduce novel diseases into their large fish populations.
7. To disinfect a tank that has housed sick guppies, fill it with water and one cup of bleach for each nine gallons of water. Let it sit for half an hour. Empty it and let it air dry. Be careful of stronger or longer dosage regimes. Bleach can eat away at tank sealants.

Quarantining new fish and maintaining optimum water conditions and good feeding practices are the best disease fighting tools at your disposal.

If the problem was water conditions, aggressive water changes usually do the trick. Proceed cautiously, reducing the amount of food you are feeding your guppies and doing more frequent water changes.

If the above remedies fail and the the guppies continue to die, the recommendation is to remove the guppies and bleach the tank.