Why are my fish dying fast with cloudy eyes? Is it water quality?

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.

I'm sorry you are having difficulties with your aquarium. There are several issues that should be dealt with right now. They are water chemistry, aquarium size and choice/number of fish. Any new aquarium should be set up and, ideally, run empty for several weeks (usually 4-6 weeks). This is so beneficial bacteria have an opportunity to populate the substrate and filter. These bacteria are necessary to break down wastes that fish will produce. The technical phrase for this is "establishing the Nitrogen cycle". These bacteria will break down wastes into ammonia then nitrites then nitrates. Nitrates can then dissipate or be absorbed/used by live plants. In high enough concentrations, ammonia and nitrites are toxic and can kill fish. Cycling a tank with fish is possible but it increases the risk of loss. Water chemistry should be checked every few days using a liquid home test kit. A water sample can be submitted for testing , but is not as convenient as testing yourself. Most pet stores or fish stores will do this for free or for a small fee. Partial water changes, no more than 30%, can be done as needed to stabilize chemistry and maintain water quality. Choices for water conditioners include NovAqua, AmQuel Plus, Prime, StressZyme or StressCoat. Tank size is another concern. With most fish, the widely accepted "one inch of fish per gallon" will be sufficient. For koi and other carp species, including goldfish, the rule is not sufficient. At full size, goldfish need 20 gallons per fish with an additional 10 gallons for each additional fish. Koi do best in larger tanks, much larger...we're talking in the hundreds of gallons or small ponds. These species produce a larger than average bio-load (wastes) that can quickly affect water quality in a tank. To combat this, large water volumes and powerful filtration are required. Any filter should be rated for at least twice the tank volume. I'm not sure what size tank you have now, it may be fine if the fish are young and small, but they will quickly outgrow it. The last issue is choice of fish. Koi and goldfish are cold water fish. They do best in water between 65F and 72F. Most species of sharks do best in the high 70sF to low 80sF. Keeping fish in incorrect water temperatures will lead to stress and illness. This could be compounded by the water quality/chemistry issues you are having currently. Until the chemistry is stable and water quality is maintained, your fish will continue to become ill and possibly die. Any treatment will not be successful in this situation. Do not purchase or add any more fish until the tank has cycled. If you have additional questions, you can post them in the forum or request a consultation to discuss the case in greater depth.

Thanks for reaching out. Not sure how when the lights were turned on, the fish responded when it had no eyes. Could the corneas be cloudy? This could be due to trauma from an aggressive fish, parasitic infestations, or infections. A veterinary visit would be recommended. If the one has no eyes, it needs to be humanly euthanized as can not find food and will starve to death or succumb to infection. Continue to test water quality and correct any problems. Good luck.

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.

If left untreated, ich will eventually kill. It can weaken the fish after which infection will set in and finish it off. It is also possible the fish were killed if a water change was done as part of the cleaning. Aged or conditioned water should always be used to avoid exposing fish to harmful chemicals, mainly chloramines, many municipalities use in treatment. Water that is not temperature matched can cause shock which will also kill fish. If can be treated by gradually raising the water temperature over 24 hours to about 85 F. Ich is temperature sensitive, this the warm water will speed up the life cycle. Once the "dots" fall off your fish, vacuum the substrate and then use a commercial ich treatment. Leave the temp at 85 F for 2-3 weeks to clear the tank. Afterwards, gradually decrease temperature to the proper temperature for your species of fish.

Check the water chemistry using 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. Rinse the filter media in tank water, not tap water, and replace it. Use only conditioned water that is temperature matched to prevent stress or shock. To limit algae growth, maintain pristine water quality via filtration and regular water changes. If possible, turn up filter flow to keep water moving. If this stresses the fish though, do not do it. Do not overfeed and remove any uneaten food promptly. Limit lighting to 8 hours daily and closely monitor water temperature as well. All these can promote algae overgrowth.

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.