My friends neon tetras are dying for an unkown reason. She has 6 in her 20 gallon long with a bolivan ram. She just did a water change, and then about 10 minites later the 2 of the tetras starting struggling to swim in the current of the filter and were floating upside down. She took them out and has them in a hospital tank. Any ideas on what is wrong with them. She is a newbie and doesnt have a water kit so i dont know her ammonia, nitrite, nitrate, etc numbers. Her tank has been up and running for about a month now without any issues.