To answer the questions first:
What size is your tank? 3.5 gallons, moved to a 1.5 gallon for isolation
What temperature is your tank? ~75 - 78 degrees
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? no
Is your tank heated? yes
What tank mates does your betta fish live with? none
What type of food do you feed your betta fish? Aqeuon fish pellets and API dried bloodworms
How often do you feed your betta fish? once a day (one to two pellets per day, with a bloodworm maybe once every other day)
How often do you perform a water change? weekly
What percentage of the water do you change when you perform a water change? 25% - 33%
What type of additives do you add to the water when you perform a water change? API Stress Coat
Have you tested your water? If so, what are the following parameters?
pH: ~7.6 - 7.8
Symptoms and Treatment
How has your betta fish's appearance changed? unsure, can't notice physical changes
How has your betta fish's behavior changed? he used to swim around a lot, especially when someone walks towards the tank. now, even with my finger close to the tank, he no longer responds and seems to be extremely lethargic, lying at the bottom of the tank (or on top of any decoration) in a sideways fashion
When did you start noticing the symptoms? about a day or two ago
Have you started treating your fish? If so, how? i added some aquarium salt (NOT epsom salt), transferred him to a smaller 1.5 gallon tank with a heater, lighting, no gravel/sand, no filter, and one decoration for him to hide in without stress; i also added the instructed dosage of API bettafix into the 1.5 gallon tank
Does your fish have any history of being ill? possible fin rot from the past
How old is your fish (approximately)? i bought the fish from petco about 8 - 9 months ago and he looked like he was a (young-ish) adult betta
I read about swim bladder disease, but his belly isn't bloated. I did notice some darkish brown fungus growing in the tank on some of the decorations and the filter, which is when I transferred him to the 1.5 gallon tank and cleansed all the entire 3.5 gallon tank with all the decorations, heater, and filter.
He's breathing pretty heavily and doesn't respond to things appearing outside the tank in front of him, including *light* taps from my finger or finger movements near the glass. He used to follow it around. He's lying sideways at the bottom of my tank, but if I give him a slight prod (to see if he can swim), he can rapidly swim away. He doesn't seem to go up for air anymore but he can (he does rarely, ever since he started acting this way). He's also not responding to dropped pellets and bloodworms.
As far as physical coloring/appearances go, he doesn't seem any different from before. I don't see any golden spots, stripes, or white cottony patches. I can only notice heavy breathing and lethargy, and maybe really dark gills.
Any ideas? :( I'd like to try to save him from an unnecessary death!