For the last 48 hours I thought my fish was was surely dying because he was laying on his side at the bottom of the tank and barely beathing. I did a water change yesterday and today he is back upright and breathing normally again, but he still can't swim. It seems like he is trying to move but the back half of his body is stiff and he can't get out of the corner. The fish is about 2 years old. The last fish I had die was probably almost a year ago and the tank mates are silver dollars, tiger barbs and gouramis. The only species that I have had died so far in my tank are tiger barbs. I did a water test with my kit before the emergency water change and the tank was normal except for the PH being slightly lower than usual (still within sae range though). Any idea what is wrong and how the fish can be treated?
Edit: Forgot to mention that the back half of the fish is a much darker color now. The normal color is grey but the back half of the fish is now dark brown.
Edit: Forgot to mention that the back half of the fish is a much darker color now. The normal color is grey but the back half of the fish is now dark brown.