I've had my betta a few months now, it was doing great. the tank developed a brown slime (not the first time) so i did a full water swap and just wiped out the slime with water and rags, and he's not been the same since. it started by just refusing to eat, and hanging out by the sides and top of the water. but now it's progressed to flopping and gasping. about 2 weeks ago i changed him to a small bowl and started doing frequent water changes, because this helped another fish i still have get better in a similar condition. but he seems to be still getting worse, not eating or pooping, and spending more time on his side at the top of the water.
on a side note, i have 3 total bettas and i did water swaps on them at the same time, they're both fine, but my big fat orange betta "Garfield" is still not doing so well.
Please answer as many of the following questions as you can. This will help us help you!
Since you have three fish, and the other two are fine, just fill it out for the sick one. When it asks for tank size, give the normal tank size, but the Quarantine Tank (QT) size would be helpful as well, for future advice on medication dosage (if needed).
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?
What type of food do you feed your betta fish?
How often do you feed your betta fish?
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?
Try to get a small submersible heater for the little guy. Bettas are tropical fish and love their warm water at a temperature anywhere between 78-86*F.
I'm a little bit confused about the water changes still. I believe I read that you're only changing the water once a week? Water changes are crucial in a tank that small, because it is impossible to cycle a one gallon. A betta can be happy in a one gallon tank (though most would argue that two gallons is minimum), but it needs heat and to be cleaned at least twice a week. Three times is ideal. Not 100% cleanings twice-three times a week. Just 50% water changes (one water change and one vacuum). This should help your boy.
One quart is not a very large quarantine tank. I would not suggest anything smaller than a half of a gallon, because most medication dosages will go by 1 gallon increments, and this makes it difficult to do accurately in a small tank (unless you are VERY good at math and are sure you won't mess up your work).
Your 1 gallon is fine for a quarantine tank. It is actually ideal, to be honest. Though, the QT you have him in now may be beneficial if he is struggling to breath.
Can you get any pictures of your fish? It would be easier to see what he looks like. If not: describe color, type, if anything is different about him. Does his fins have black or gray singed ends that were not there before? Do they look like they have been squeezed together (clamped) and not spread out? Are they torn? Are there chunks missing? Does it look like he has a bulge behind his gills (where his stomach would be)? Where is he in the tank a majority of the time?
If you can answer as many of these questions as possible, it would help. Pictures are really the best thing you can provide. They offer a lot more help than simple description. Even a phone picture is fine. It doesn't need it be fancy.
As PP stated, they are tropical fish, 76-82 degrees is ideal. Also, with a 1 gallon tank, you should be changing the water a minimum of 3 times a week.
Also, you said you wiped out the tank with rags. Is it possible you've contaminated your fish with detergent? It's highly recommended that if you wipe your tank with anything, it be with a material that has NEVER had contact with any type of soap or cleaning agent. If you cleaned his tank out first, the residue would have ended up in his tank, and the other fish would not have been contaminated.
You need to do this today: Run everything in the QT under hot water. Run everything in his original tank in hot water (including rocks; use a strainer or colander). You're going to use his original tank with nothing but rocks at the bottom, and only fill it half way.
Now, I hope that you will have a submersible heater tonight, since it really is a necessity (chain pet store employees have a knack for telling costumers false information about bettas, like no heater is necessary). It doesn't need to be adjustable. The ones that adjust to room temperature are the only ones that will fit 1 gallon anyways. So, you'll have that in there as well, under the water of course.
Then, you'll put half of a teaspoon of epsom salt in the water and mix mix mix. Make sure it is dissolved before your fish is put back in there. Make sure you are using epsom salt.
Use water conditioner!!!!
Stress coat works nicely as well, if able to get it. It is literally called stress coat.
Now acclimate your fish.
Slowly float your fish in a cup inside of his tank. Put spoonfuls of his tank water into his cup over a fifteen minute period. You don't need to put in a ton of water into the cup, just make sure he gets used to the mixture. After about fifteen minutes (or take as long as you need - fifteen is the minimum), you can put your fish in there. Try not to let any of the old water get into the tank, though. I usually use a spoon to softly coax mine out of the cup. The cup is tilted, and he just jumps into the bowl on his own.
The reason you do not want to feed him for three days, is so you can monitor his poop. Make sure he is pooping. He may simply be constipated. He looks kinda clamped, so it may be swim bladder disease. Though I'm willing to bet that he's constipated from the cold water and slower water changes. I hope that all of this info helps!!