Urgent - Betta With A White Mouth

Hello All,

I have a female betta in a 15 gallon tank. All water parameters are normal. I have one of those little thermometers and it says it is 79 degrees, but i've heard they are unreliable. I introduced some Corys to the tank yesterday and it did not go well. The betta was very violent and immediately killed one Cory. I removed all of the Corys and returned them to my Local Fish Store. They are A-OK (Except the one). Today, my betta is very lethargic, constantly going for air, and has a white mouth. I know there can be a white mouth fungus that causes issues, but i'm also concerned that maybe she hurt her jaw?

Here are pictures of her:

Thank you so much!

 

I couldn't really see much in the picture, but it's likely cotton mouth/some kind of fungus, my best guess would be that the cories introduced it, although they were only briefly in there just yesterday, so I'm not too sure. It also could be ich, does it look fuzzy or like a grain? Do you have any way of accurately reading your temp as that may become important. If you know the thermometer is unreliable, why not get a quality one?

 

I had no idea the thermometer was unreliable until I started researching what is wrong with my betta. I intend to go out tomorrow and get a more reliable thermometer, but all the shops are closed at 6 PM on a sunday, and it is currently 8. It doesn't really look fuzzy or grainy. It is just white. I have put her in a 3 gallon quarantine tank and I added some Bettafix. She is spending a lot of time angled, and not horizontal. Thank you for trying to help. If she is treated with the antibiotic, should I assume my main tank is contaminated? What should I do? Remove everything, bleach it, start from scratch?

 

She probably impaled herself on a cory spine.

For future reference, just in case, you need to quarantine all new arrivals for at least a month to be sure they're free of disease.

She probably just needs clean water to heal, so I'd personally put her back in her tank.

 

Thank you. I will be 100% sure to do that in the future. That makes perfect sense. She was super aggressive so she may have gotten jabbed. I don't want to stress her out so I'm going to leave her where she is with the medicine for a few more hours (maybe overnight) and I'll stick her back in the 15 gallon. My poor little girl. I'm so worried. She isn't eating at all, but I guess that makes sense.

Edit: In an effort to make myself feel better about the thermometer thing earlier, the temperature on my heater matches the temperature indicated on the thermometer.
Edit 2: Things appear to have taken a turn for the worse. Her face is getting whiter and she is more lethargic. She was gasping for air at the surface, trying really hard to push her entire face out of the water. I don't suspect she is going to make it

 

Ah okay, gotcha, thermometers are such a pain, I only use the digital ones, I find even the glass ones to be junk. Definitely agree with the above, forgot to mention that, if possible, always make a point to quarantine, you don't even need an aquarium, I have some buckets (fish safe used to mix my saltwater) and I set them up with filter, heater, etc. just like a tank. If she's rapidly getting worse, I'm guessing it was probably an injury like what was brought up above, I would assume one of them probably got her pretty bad, are you able to get a closer look at her? Something like ich or a fungal infection typically won't cause them to rapidly decline over the course of a day. I wouldn't move her around at all, she'll just get more stressed, what type of medication were you using?