Help With Neon Tetras!

Problem with one of my neon tetras. We have a 10 gallon tank, with a Betta (had for 1 1/2 years) and 6 neon tetras had since August. One of my tetras looks very rough. Grayish color, back tail fin completely gone. Swimming and eating seems normal. We had a brown algae problem recently, but I removed the object that was mostly covered and replaced it, and treated the tank for algae overgrowth. At that same time we had a plant that seemed to have some type of disease (bleached leaves, black/brown algae looking spots) I pulled it out and replaced it too.

Not sure what I need to do to help my fish. Any advice is welcome. Thanks!

Here is a picture

 

Looks like someone is beating him up. Id guess the Betta.

Also, Neon Tetras and Bettas aren't really temperature compatible. Neons really need 72-75, Bettas need 80-82. If you're keeping the tank at Betta temps, that could also be a problem for the Neon.

 

The tank is currently at about 78.

It could be George(the Betta) but he has not bee aggressive at all since we got the tetras. He mostly ignores them. He is very non aggressive and very rarely flares up, even when we have put a mirror by him for a bit.

 

Looks like it might be fin rot. Watch the your fish, an make sure to see if your betta is showing aggression or bullying the tetras. Looks like fin rot to me though. I would buy a small hospital tank for him to isolate him. Then use Melafix that should work good for fin rot.

 

I agree that it's fin rot. I would recommend doing daily water changes for a week or two if you're up to it before you treat with anything though. My betta had fin rot and frequent water changes fixed it in no time

 

I agree that it's fin rot. I would recommend doing daily water changes for a week or two if you're up to it before you treat with anything though. My betta had fin rot and frequent water changes fixed it in no time

What percentage of the water should I remove for the daily changes?
Thank you all for your help!

 

When this happened to me I just did the usual 20/25% but daily instead of weekly

 

I'd get it out a.s.a.p. and euthanise.