Infection on Cory catfish mouth
I have a julli Cory catfish that was fine this morning and all of a sudden has a white cloudlike film on his mouth and is really struggling. I'm not sure what to do.
1) Is this fungal or is it columnaris? Based on pictures I've seen it appears to be fungal but please help me understand this.
2) Based on that information, how do I treat him? Do I remove him and just treat him? Do I treat the whole tank?
3) Regardless of whether he makes it or not, how do I prevent this in the future? I clean the gravel and do partial water changes every weekend to keep my tank clean. Do I need to treat the tank with something to kill the bacteria or fungus?
My tank parameters: 36 gallons, ammonia is 0.25, nitrite is 0.25, and nitrate is 5-10ppm. I know this means my tank is not fully cycled. I didn't have great information when we started the tank and am now trying to deal with the cycling the best I can. We had an ammonia spike about a week ago and have since done several water changes and am testing the water every day and treating the water with prime.
Any help would be appreciated! I really want to get this under control so it doesn't effect more fish in the future and take out my whole tank.