[I have no idea.]

On 7/18/2022 at 12:45 AM, colo3000 said:

Deep cleaning the tank and tank decorations most likely only resulted in you removing any beneficial bacteria that was helping your fish. In your post it didn't look like you mentioned doing any water changes. 3 gallons is on the small side for a betta, and adding the plecos is definitely going to make the situation worse. If you do not know about the nitrogen cycle, read this article. You should buy a water test kit as well so you can determine whether the water quality is good or not. Placing it in a tiny bowl like that to "quarantine" it also does way more harm than good. Ammonia, nitrite, and nitrate levels will rise much faster, hurting your betta more. When your betta is the only fish in an already small tank, there is no reason to take it out and quarantine it.

Ok. Thanks for the info. 

On 7/18/2022 at 1:10 AM, nabokovfan87 said:

Welcome to the forum, it's awesome to have you here!

I would suggest starting any fix by checking this article and video out:
https://www.aquariumcoop.com/blogs/aquarium/betta-fish-care-guide
 

A few notes and some questions.  Where is the tank, would something larger (10G or preferably a 20L) fit in that space?

Are you testing the water in any way?  Please watch this video for a good breakdown of why this matters so much.
 

Lastly, what is your normal schedule for maintenance in general? Do you have the tools needed to clean the tank?  Typically this is a bucket, siphon, and dechlorinator. 

I have ph strips but haven't gotten anything for the nitrates or nitrites. I do about a 1/3 water change every 2 weeks with dechlorinated water. I don't have a siphon. There's probably a bucket in the garage. I'll watch these videos, thanks!

[I have no idea.]

This is a long story, heads up. My male betta, Swim Shady, started out at the bank I worked at. That was last April 2021. He grew great and was lively and happy. No problems. We had a 3 gal aquarium with no heater and the filter that came with it. Nothing else in the tank with him. And no live plants.  And the water stayed clear so we never changed it. Just being honest. After awhile, like October/ November 2021 I read that he was tropical and would like a heater and some plants. So I started with 1 tall plant and 1 short plant and some moss. No problems. Then I bought a heater and put it in. Non adjustable. Brought the temp up way too quick. I learned my lesson there. But Swim was in bad shape. Losing fins, gasping for air on the bottom, lethargic, not eating. Had a fight with a coworker and ended up bringing him home. He was in a smaller bowl for transport. I refilled the tank and let it settle for a couple days. Added Swim back to tank. He started acting right and eating and his fins got somewhat better. So I didn't mess with a heater for several months because I was terrified. But in February I could tell it was too cold for him. I bought an adjustable heater on Amazon. I religiously checked the thermostat to make sure it wasn't too hot, and only raised it 2 degrees every other day until 76 degrees and I left it there. Swim has been completely fine. He eats, swims, plays in his hollow log, responds to my voice (I think). But his fins are still almost completely clamped and i have no idea why. If that's as good as they're gonna get then that's fine but i don't want him to be hurting or sick. I did move him to a small quarantine bowl, treated him with bettafix for 1 week, completely cleaned his tank (took everything out, cleaned the rock and sides). There was no difference in his fins. I added 2 plecos. There are some snails that have appeared, none are very big. I'll attach pics of his original fins and now.

The pics posted out of order. 3rd pic is original. 1st pic is after heater mess up. 4th pic is bettafix treatment. 2nd pic is back in tank