What's wrong with the poor dude?
I tried treating for fin rot and hasn't improved. I've been treating that for 2 weeks?
Tank size? Water quality? Heater? Filter?
He needs a filter asap. With a water change only once a week there's very little to 0 oxygen in that water.
Are the nitrites 50 or the nitrates 50? Either way it's too high and needs a water change.
No fish can survive with little oxygen in the water including bettas. Their labryinth organs allow them to live for a short period with no oxygen. Bettas survive without a filter it does not mean they are thriving. That's like saying humans can live without food--while we can it doesn't mean we should.
A filter also removes toxic buildup like ammonia and nitrites.
This is not true. Don't listen to this person.
Bettas like all other fish take in oxygen through their gills.
I'm confused as to why you believe this not to be true?
I've been told, and I've seen it in person, that Betta's come up to the surface, take in a big gulp of air, and then swim back down. I've seen it with my own two eyes.
Let's just agree to disagree guys, this isn't the place for a debate.
Also, has he always looked like this? The nitrites in the water are not great, they should be zero.
Bettas can take oxygen from the surface as supplemental oxygen. They still need it in their water source as they intake their primary oxygen from their gills. I encourage you to do more research on this since many new fish keepers believe bettas do not need filters. I myself thought that to be true until truly reading information and researching.
Got him in a 4 gallon tank without a filter. Water change once a week.
Nitrates - 0
Nitrites - 50
No heater but he lives in Singapore so water is at 28
This is not what I've heard. My best friend works at a Petsmart. He says that the Betta bowls have no Oxygen and they only change the water once a week. Those little water bowls barely fit the Betta in them.
Your friend getting hired by a chain store doesn't mean he/she knows anything about fish. The goal of big stores like petsmart, and most any fish store that isn't a small mom and pop type place, is to receive the product, display it in a way that takes up as little space and requires as little maintenance and resources as possible, and get it sold as quickly as possible. It's not their concern whether or not the fish can live long term in a cup, it benefits them if you kill them with unfiltered, uncycled tanks or bowls and go buy a new one in a few weeks or months, more so than if your one betta lives for years like it should if you give it what it needs to be healthy. Those stores throw away dozens of dead fish every day because it's cheaper than giving every betta a filtered tank. It's pretty sad to me, the reason bettas are sold in cups is because they sell so many that it's the only practical way... And the only reason they sell so many is because misinformed people think it's acceptable to keep one in a tiny bowl or a vase with no filter or heat.
From that pic there is a lot of food in there. Maybe parameters are off. But I'm not sure my betta has the same issue. But I have a filter, I check my parameters every other day. Treated him for finrot. Do weekly waterchanges. No tank mates. So idk. I'm struggling with the same issue.