My fish keeps dying. What caused it and how can I prevent it?

Hi and thanks for your request. this ''fluffy'' material on the skin fish is likely a oomycetes (a fungus basically) called Saprolegnia. This is a secondary proliferation due to a primary infection which could be due to a variety of causes unfortunately. From the pic white spot disease (ich) dies not seem to be present. Given the high mortality incidence it is absolutely necessary to check water parameters and make sure they are normal and take the moribund fish (and the dead ones) to your local veterinarian for (euthanasia if needed and) necroscopic examination. Your local veterinarian will be able to tell what is going on or possibly prescribe some treatment (likely antibiotics or disinfectants).

Im sorry for the loss of your fish. It could be, but without an exam it is difficult to say definitively. Some fungal or bacterial infections are contagious. Monitor the other fish for similar symptoms. Maintain pristine water quality and consider an "all-in-one" treatment if necessary. You can find these treatments in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Infection, old age, poor water quality or poor nutrition are all possible causes. The "wound" may have been post mortem, caused by being eaten by tankmates. Monitor tankmates for signs of illness or infection (red spots, fuzzy spots, swelling, lack of appetite/activity, etc.). Submit a water sample for quality testing or use a home kit to test for chemical imbalances. You may need to perform water changes, treat with chemicals or treat with antibiotics or antifungals depending on symptoms. You can request a consultation to discuss the situation in more detail.

I am so sorry that you are having this problem! With multiple die offs of fish, one of the first things to consider is that the water quality may need to be addressed. I didn’t see you mention in your post whether you have been able to assess that or not, but it would definitely be something to evaluate. Things like high ammonia, high nitrites, and high nitrates can be devestating for fish. Also, if your filters are not working properly, or are not in the correct set up, that can also contribute to fish death. From the clarity of your water and the lack of substrate and tank furniture, it makes me more suspicious of this contributing to your issues. The other major reason for multiple fish deaths are infectious diseases (bacteria, parasites, fungus) - but ideally these would be diagnosed by a veterinarian. There are many over-the-counter medication treatments at pet stores for these, however they can be damaging to your water system, so ideally would not be used unless you know the problem that is going on.

Loss of color in fish can be a sign of severe stress. Stress can be brought on by disease, poor water quality, over cleaning the tank (too frequent or too large water changes), over aggressive fish, poor or inadequate nutrition, being moved, over crowding, and a host of other situations. I recommend that you start by reviewing your water quality and tank environment. How are your water parameters? Review how often you do water changes and how much water you change at one time. How much are feeding? Could you be over or under feeding your fish? Is there a bully fish in your tank - a fish that chases or aggresses against other fish. Are the number of fish in your tank suitable for the size of the tank? Look for signs of disease. Fish can suffer from bacterial, viral, fungal, protozoal, and parasitic infections, but not all species of fish suffer from the same illnesses. You can find charts of fish diseases in books or on the web to help you narrow down what illnesses might be affecting your fish. Treatment of disease will be based on determining what type of organism is making your fish ill. To prevent illness in fish, maintain high water quality, avoid over crowding your tank, and quarantine new fish before introducting them to your tank.

Check the water chemistry. The discoloration could be due to elevated ammonia levels which can cause "burns". Use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. The Neons (blue fish) appear to be infected with Ich, a parasite. Treatment is possible with commercial products found in the local Petco. Follow label directions carefully. You will need to treat the entire tank until all traces are gone. Removing a lump from your fish on your own is never recommended. You can cause severe injury. Most broad spectrum antibiotics (Kanaplex, Maracyn, Maracyn 2, etc.) found in the aquarium section of the local Petco should help treat or prevent infection. Choose one and follow label directions. Remove the carbon filter insert during treatment if indicated. Maintain pristine water quality via filtration and regular partial water changes to aid in recovery. You can feed frozen worms, just thaw then first in a small cup then place them in the tank.

Sorry for the problems. Intestinal parasitism can affect small fish. Please check water quality to ensure ammonia, pH, nitrates and nitrites are appropriate. Taking a fish to a veterinarian for identification of the parasite can lead to a treatment plan for the adults. Sometimes invertebrates (snails) are intermediate host for the parasites, and removing them can reduce the problem. Good luck.