Fish emergency!!

[Andy Sager]

Dizzy it was probably an ulcer

Unfortunately, the position, reaction and timing don't correspond with this diagnosis. Ulcers don't appear overnight nor do they do that kind of damage in that short amount of time. The picture clearly showed a "slime" like condition prior to the flesh loss. A severe bacterial disease ( most likely extreme Columnaris) was the cause for this fish.
You may want to check out this link for a site on disease diagnosing and treatments. It may help in your own tanks and fish as well.
Chart on Fish Diseases, Symptoms and their Treatments

 

[Dizzydea]

Well thanks everyone for your help! It sucks when you do your best but with no luck . I worked a long day and will call the pet store tomorrow. Andy I will also get meds you suggested as well. I will treat my other fish to.

 

[Andy Sager]

Well thanks everyone for your help! It sucks when you do your best but with no luck . I worked a long day and will call the pet store tomorrow. Andy I will also get meds you suggested as well. I will treat my other fish to.

Let's hope you never need them but they are good to have if you do

 

[threnjen]

I opened this and saw the first picture with the saddle sore and thought columnaris, then read the whole thread and seems lots of people agree on that.

Don't buy any other fish that shared water with this one. That is a very nasty strain to have taken him from a sore to a massive chunk missing overnight.

Columnaris is seriously the worst. I would treat that other fish with the kanamycin + furan 2 just to make sure he is fully nuked of it since he shared water. But it sounds like other people already recommended this so I'm just kind of repeating lol