White mouth

Hi. A while ago (perhaps thee-four weeks) I purchased a few emperor tetras. One of them either has some damage or deformed mouth, it doesnt align properly, but I think it's mostly cosmetic and does not create problems. Hard to say if its genetic or injury because some of the other males had bitten off dorsal fins already at the store. She can eat ok though. And the fins on the other fish are healing ok and are happy and very active. I noticed the mouth became more white after a while and stayed like that. Then I had an outbreak of ick, so I treated that successfully with Sera Protazol. Hopefully I got it all, its around a week ago. But the white remains on her mouth. Hard to keep track of time but could it have been white on mouth for around 1,5 weeks? I'll add picture but I could not get good one. It's just on the surface and is not fluffy. I've been told in a Facebook group its gram negative bacterial infection and treat her with Metroplex and Furan 2 but I would like second opinion. I know its hard because of my bad pictures, sorry.

I can only get Sera and JBL here but I suppose they have similar medicines.

Tank parameters are:
pH 6.8
gH 3
nitrite 0.05
nitrate 5-10

I know nitrite should not be present, could it be because of the medicine?
Nitrate 5-10 is probably ok since medicine instructions was do 80% water change.
and perhaps hardness should be around 5, I could remove some driftwood but first things first

I have an external filter eheim Classic 250 thats been running for around a year but only one month in this tank since I upgraded. Tank (juwel 180) also has internal filter thats been running for this month

Columnaris (mouth fungus) is a nasty flesh eating bacteria that spreads very quickly and most fish are usually dead within 24-48 hours of noticing the white mouth. If you haven't added any new fish since you got the emperors, and if the fish has had it more than a week, then it is unlikely to be mouth fungus.

Metroplex and Furan 2 are anti-biotics that will wipe out filter bacteria and can be used on confirmed bacterial infections. However, I don't think this is anything to worry about, and I would not use anti-biotics in the tank.

It is probably bruising from bumping into the glass or other objects in the tank. Basically the fish has a fat lip.
Monitor it over the next week and if it gets worse rapidly (within 24 hours), and spreads across the face, head and gills, then get back on here with another picture ASAP, otherwise leave it.

Right now I would wipe the inside of the glass, do a 75% water change and gravel clean the substrate each day for a week. That will help improve any health issues in the fish and also reduce the nitrite. And clean the filter if it hasn't been done in the last 2 weeks.
Make sure any new water is free of chlorine/ chloramine.
Then monitor and see how she goes.

Thanks for the quick reply Good to hear its not columnaris. It could just be that her mouth is sensitive or injured, i hope, then it can perhaps heal. I just moved her back to the tank I upgraded from, 100 liter, and put a cycled sponge filter in it. She is probably stressed and not feeling ok because she kept chasing my Cardinal tetras right now, never seen that before. Another thing that I did not expect is that the males would be this aggressive, they constantly chase other males and often females too. I have 4 males and 5 females, is that too much for a 180 liter? It's pretty heavily planted and I plan to grow more plants so I thought it would be good I have a feeling 2 males and 7 females would be better genderratio too

In my experience, Emperor tetras are not overly aggressive and don't go around biting each other. You have 9 fish and they shouldn't be hassling each other.

The fish you have will be fine in the 180 litre tank. You could add more if you like.

Do you have a picture on the back of the tank?
If not perhaps put something on the back of the tank to make the fish feel more secure. Most aggression from tetras is caused by stress of being in small groups or not having enough cover. Having a tank without a picture on the back might be a contributing factor.

Make sure the water is good and feed them 3 times a day if the filter can take it and see if the extra food helps. If it doesn't help then it could be they are just settling into the new tank and re-establishing territories.

it is a columnaris strain that affects only tetras, they have that plus the normal strians of columnaris to fight in their lives, it could be either or.