Never mind. He passed away [emoji22]. All levels are within range. My my other tetra has deep red gills why would that be?You're going to have to provide a bit more information about the fish, what's going on, how long you've had it for, where it lives, etc. A one minute video would help too if it's swimming unusually. You can upload videos to YouTube then copy & paste the link here.
Okay, but it's only this one fish. Does that make a difference?bright red gills is usually poor water quality or something in the water poisoning the fish.
do a 75% water change and gravel clean the substrate every day for a week. see if it helps.
make sure any new water is free of chlorine/ chloramine before it's added to the tank.
The water change looked to helpsome fish are more susceptible to things in the water than others. Even if it's not poor water quality, a big water change and gravel clean will dilute disease organisms in the water and reduce the chance of other fish getting sick, especially considering you just lost one.