Betta fish death

My sises betta fish died tonight. he was a dear friend of ours. but what confuses me is how. all of the scales on his side were raw and bloody. i had noticed a slite cut on his nose but all of the sudden, out of no were it spread all over his body. we also just recently got him a new filter and we are wondering if that was the cause of it. any feedback would be great. (sniffle):tears:

There are several dieseases that could be the cause. I doubt it would be the filter, unless the filter was not cleaned, or was contaminated somehow.
It could very well have been a bacterial infection, which can become advanced very quickly. Sorry to hear of the loss of your pet.
I'd reccomend full sanitizing of the tank and all equipment if you plan on getting another fish for that tank.

yeah i have a feeling its scale rot

Scale rot usually happens after fin rot, and you didn't mention his fins rotting off. Dropsy is another betta disorder, but it's not normally associated with sores, while bacterial infections are.

How large of an enclosure was he given? I think the minimum for a betta would be a 5 gallon tank, better at 10 or more.

It also could have been bacterial like mentioned above, fungas, chemical contaminates or he was already sick when you got him.

Betta fish are just about the most abused fish out there next to goldfish and not given the best start from large and small pet stores that keep them in a cup of blue water.

They are a tropical fish and need warmth, slow moving filters, good airation just as much as the next tropical fish. Just because it's fresh water doesnt mean it can handle room temps and thrive.

awe poor little guy. I had two betas that lived for over two years each in about 8 gallon matching vases. I loved those little guys. I'll get more someday.

Yeah he was in an 8 gallon. but what was weird was that this happened to him within an hour or two.

I was always taught that the small bowls that they are in, are good for them. Since in their native Siam, they live in small pockets of water in rice paddies. I thought that larger tanks stressed them.. and I know that being with any other fish puts them on edge.
Sounds like a fungus to me. Coppersafe always helped me clear it up if it ever started in my Oscars; carried in on feeder fish I am pretty sure.