What kind of water do you use for neon fish?
Neon tetras prefer soft, acidic water with a pH between 5.0 and 7.0 and a hardness level below 10 dGH. They are sensitive to changes in their environment, so it's important to keep the water parameters stable. You can use purified water from a filter if available or use water-treatment additives which adjust water qualities to the ones mentioned to ensure that the water is well-oxygenated