Help I don't know what's on my betta

[Lbou18]

My betta has developed this thing in his side. I am not sure what it is or what to do about it. If anyone has knowledge please let me know! He doesn't rub on his plants and he doesn't clamp his fins when he is around in his tank. He is very active still and hasn't lost a lot of color and still eats regularly, and it has been almost two weeks. I do have a small 5watt heater in his tank, is it possible it is a burn?? I attached pictures below
Please help I love him a lot and don't want him to die

 

[LarsB]

To me it looks like a wound, but could be fin/scale rot. Hope it is NOT SFR, I treated the water with aquarium salt.
I am no expert, but back in 2015, I had a older male, had an eruption further up his "shoulder", looked like a pimple. Soon it popped and he was completely infected, scales AND fins deteriorated and fell away. He was lethargic and not eating. My mostly dark blue /purple boy turned pink and lost his blue, except on his face and the rotted edges of his fins. Some one, very knowledgeable, told me he would most likely not make it. SLowly, he just sat in his home and I could not out him down, but he did not seem to he unhappy, just very still. After 8-10 months from the beginning, he was closer than ever to moving over the bridge, and I brought home his "replacement", he was NOT having that.... His name was Rumble (Rumble Two, actually) and then enter Grumble. Ticked of my Rumble and he began flaring, chasing at that other guy, show him gill covers and, low and behold, Rumble began to eat, just to live and drive Grumble away! With in a month Rumble was getting some color back and even built a nest, after the addition of a 3rd boy, Gorg, to the mix, but all in separate containers.

Rumble survived another few months after that, but was a good 15-16 months after we thought he was a lost cause.... Rumble The Ruff and his nest (he was about 5.5 years old + when he passed)
Grumble,
Gorg, (AKA Gorgeous)
Rumble, Grumble and Gorg (Back to front)
Vick (AKA Vicious Fischious)

 

[Retired Viking]

To me it looks like a wound, but could be fin/scale rot. Hope it is NOT SFR, I treated the water with aquarium salt.
I am no expert, but back in 2015, I had a older male, had an eruption further up his "shoulder", looked like a pimple. Soon it popped and he was completely infected, scales AND fins deteriorated and fell away. He was lethargic and not eating. My mostly dark blue /purple boy turned pink and lost his blue, except on his face and the rotted edges of his fins. Some one, very knowledgeable, told me he would most likely not make it. SLowly, he just sat in his home and I could not out him down, but he did not seem to he unhappy, just very still. After 8-10 months from the beginning, he was closer than ever to moving over the bridge, and I brought home his "replacement", he was NOT having that.... His name was Rumble (Rumble Two, actually) and then enter Grumble. Ticked of my Rumble and he began flaring, chasing at that other guy, show him gill covers and, low and behold, Rumble began to eat, just to live and drive Grumble away! With in a month Rumble was getting some color back and even built a nest, after the addition of a 3rd boy, Gorg, to the mix, but all in separate containers.

Rumble survived another few months after that, but was a good 15-16 months after we thought he was a lost cause.... Rumble The Ruff and his nest (he was about 5.5 years old + when he passed)
Grumble,
Gorg, (AKA Gorgeous)
Rumble, Grumble and Gorg (Back to front)
Vick (AKA Vicious Fischious)

You did a very good job keeping him alive for over 5 years, the average is 3 years.

 

[LarsB]

TY! I have had several boys that have made it 5 or more years (my record was almost 7 years) but that was always in smaller bowls, live plants and "dirty" conditions, but some peoples standards, but more like their ancestors environment. The light was on almost 24/7. though the plants were so that I doubt he noticed bright light.
Then the internet and FB kept saying they do better in a tank, with other tank mates and larger volume of water, filtration, etc... so each of my boys got a 10 gal planted tank. and tiny roommates.... None of them (my 4 males) lasted a year, though the tanks were healthy and have been great for other fish (BN plecos, tertas, corys,)
After that I set up a 29 gal, sorority tank, 5 ladies (one wasn't), so the 4 girls (bluie caboulie (pic), croan, mean green jean, and Bruja roja bre did great, but again, fleeting joy, the last two made it almost 16 months...
These were all commercial big box store fish, girls were purchased as babies....
I think the imported bettas are just weaker now than in years past. I know 35 years ago, you could get fish at the shops and actually be able to condition them and breed them.
"show" bettas sold at the big box stores now, are prob 50% into their life span

 

[Retired Viking]

I kept mine in a 5 gallon tank with heater and filter, they lasted on average little over 3 1/2 years. It has been many years since I had one. They are an enjoyable fish.

 

[Colin_T]

it's a wound or ulcer.

do a 75% water change and gravel clean the substrate every day for 2 weeks.

if there's no improvement after a week, or it gets worse, then add some salt (2 heaped tablespoons per 20 litres).

if it doesn't improve after a few days of salt, add a broad spectrum fish medication that treats fungus, bacteria and protozoan infections.