My fish is turning black and discoloring. Is it sick or stressed?

Elevated ammonia levels can result in "burns" which may turn fins and scales black. Use a home test kit or submit a water sample for testing. Most pet or fish stores will do this for free or for a nominal fee. If ammonia levels are elevated, daily partial water changes, using aged or conditioned water, can decrease ammonia to safe levels (0.25 ppm or less). StressCoat or plain aquarium salt (NOT table salt) can aid in healing. Dissolve 1 teaspoon of salt per gallon of water into a cup of tank water and gently pour it into the tank. Confirm adequate filtration. The filter should be rated for at least twice the volume of the tank. You can change 20-30% of the tank water every couple of weeks. Use only aged or conditioned water that is temperature matched to prevent stress or shock.

Black spots or discoloration can be caused by elevated ammonia levels. Test water chemistry using a home test kit or submit a water sample for testing. Most pet or fish stores will do this for free or for a nominal fee. Ammonia and nitrites should be 0.25 ppm (parts per million) or less, nitrates can be 40ppm or less. Partial water chnages daily should be done to decrease ammonia levels. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Elevated ammonia levels can be caused by overfeeding, new tank syndrome or overstocking.

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.

Thanks for reaching out and including pictures. Darken scales can often be a reaction to a water irritant. Check water quality such as pH, ammonia, nitrite and nitrates, and correct any concerns. Darken scales can also be a result of poor nutrition or some metabolic concerns. Since he is sitting on the bottom of the cage, it is concerning that he is sick. If the water quality checks out, a veterinary visit is recommended. Good luck.

It looks like a species of gourami. Most can be kept in a community tank with other fish. The black may be caused by high ammonia levels. Submit a water sample for testing or use a liquid home test kit to check chemistry. Ammonia can kill fish if levels are high enough. Partial water changes can be done daily to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. My preferences for water conditioners include AmQuel Plus, NovAqua and StressCoat.

This could be ammonia burn. Check the water chemistry. 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 a nitrate level of 20 ppm or less. Partial water changes will be needed to stabilize chemistry. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Goldfish are cold water fish and do best between 65 F and 72 F. When using an ammonia reducing product, be sure to test the water after treatment but before pouring the treated water into the 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.