My betta is sick after a water change. Is it temperature shock?

When performing water changes it is recommended to change about 15-25 %of the water. His helps keep some of the good bacteria in the water as well as decreases dramatic temperature changes which can cause significant stress on the body. I suspect that it is the temp change that is hard in him, however if a dechlorinator was not used in the water then that could be problematic as well. If you feel that is the case please Add a dechlorinator. I hope he improves!

The ideal water temperature for bettas is between 78 F and 80 F. Check water quality and perform a partial water change if necessary. Used aged or conditioned water that is temperature matched to prevent shock or stress. If he won't eat pellets, try soaking them in a bit of garlic juice. This can serve as an appetite stimulant as well as an immune system booster. You can also offer freeze dried (or live) bloodworms, brine shrimp or tubifex worms. The "wiggling" when he swims may be normal for him but check his fins for signs of fin rot which can make swimming more difficult.

Drop the water temperature to 80 F. Bettas do best between 78 F and 80 F. The higher temp likely did not cause her death, but warm water holds less oxygen than cooler water. She may have been ill or old. She does appear bloated in the image. It may have been dropsy or other infection. Monitor water chemistry using a liquid test kit. They are more accurate than the strips. Tou can also submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with nitrates at 20 ppm or less. Try to keep the pH as close to 7 as possible. Bettas can tolerate acidic water, but changes should be gradual to allow time for acclimation.

I would recommend to change his water again and make sure you have a water conditioner that is not expired. I would also recommend to upgrade Smitty to a 3-5 gallon aquarium with a filtration system and a light. These tanks tend to create a healthier environment because the water is moving. You could add in live plants to provide a little extra oxygen. I hope Smitty starts feeling better!

Cold water can affect activity in fish. Bettas are tropical fish and do best between 78 F and 80 F. Check the water chemistry also. You can use a home test kit, such as the API Master 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 a partial water change if necessary to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Diet can influence color, so it is possible this is partly to blame for the color change. There are diets that can be fed to enhance colors.

Recheck water chemistry to confirm 0 ppm ammonia and nitrites with nitrates at 20 ppm or less. A pH of 7 is fine and they can adjust to more acidic water as long as the change is gradual. Temperature should range between 78 F and 80 F. Plain aquarium salt (NOT table salt or epsom salt) can be used as a general tonic to reduce stress, improve gill function, treat minor infection and aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup or two of tank water and gently pour it into the tank. Perform partial water changes every couple of days to maintain water quality. Treat only the volume of water being replaced. Treat with aquarium salt for no more than 14 days then reassess the condition. An antibiotic, such as kanamycin or erythromycin, can be found in the aquarium section of the local Petco if the salt treatment doesn't help. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Bettas are tropical fish and do best in water between 78 F and 80 F. A heater is typically required to maintain stable temperature. Rapid fluctuations in temp can be stressful. You should also check the water quality and chemistry. Poor water quality can cause the symptoms described. Filtration and regular partial water changes are necessary to keep a tank clean.