Betta With Swim Bladder Disease? Question

I've been having a problem with my Betta named Rusty. I estimate him at about 3 1/2 years old.

Recently I set up a biotope aquarium for him. It has Fluorite substrate, driftwood, and various plants. I used spring water to fill the tank (the same spring water I use for my shrimp tank and have been using for years). The only addition I added to the spring water was Instant Amazon for his tank. It took about a month before the tank was fully cycled (GH: 120, KH- 40, PH- 7.0, No2: 0, No3: 0) and I put him in it. It is a fluval spec 2.6 gallon.

Previous to his new biotope tank, his old tank had become overrun with green hair algae so I scrapped the current tank and housed him in a large glass jar until I could prepare his new home.

When I put him into the new tank, he seemed to be doing pretty well and especially seemed to enjoy hanging out in the water lettuce roots. I did weekly water changes of 20% with the same spring water dosed with Instant Amazon. There is no heater because he is in my office and with it being summer, the house is only cooled by window air conditioners that are in the living room and bedroom. I keep my office door closed and the tank maintains a temperature of about 75 degrees.


However over the past few days, he has really struggled to get around and has been lying on the aquarium floor. I removed him from the tank and currently have him in a small plastic bowl. He seems to be exhibiting symptoms of swim bladder disease but I believe it has gotten progressively worse. He is not eating and struggles to swim in any direction. I don't believe he has TB since he is not swollen and his scales are not raised. I also do not believe it is due to overfeeding since I only feed him a few bio-gold pellets at a time and have never seen him with an extended belly.

This is him today. He barely moves and his body is at that weird angle. That is not poop in his bowl, those are bio-gold pellets I've tried to get him to eat. He might take one but then spits it back out after a few seconds. I have since removed the uneaten food.

Looking for advice for treatment and to identify if he might have something else going on. Could it be hereditary or due to old age?

Thanks.

 

Here is a good article that pretty much goes over everything