First the questions Answered:
What size is your tank? 1.5 gallon
What temperature is your tank? Room Temperature (70 or so)
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? No though the filter is "oxygenating"
Is your tank heated? No
What tank mates does your betta fish live with? Only himself
What type of food do you feed your betta fish? TetraBetta mini pellets
How often do you feed your betta fish? 2-3 pellets twice a day
How often do you perform a water change? twice a month
What percentage of the water do you change when you perform a water change? 100%
What type of additives do you add to the water when you perform a water change? Tetra AquaSafe
I have not tested the water.
Symptoms and Treatment
How has your betta fish's behavior changed? He seems to be having trouble swimming and has become melancholy, hiding in his little skull-hiding place and staying there, or hiding behind the filter.
When did you start noticing the symptoms? Yesterday night around 12 midnight
How old is your fish (approximately)? I bought him around 2 months ago
Now, what seems to be wrong: Cornelius (the betta) is having a lot of trouble swimming. His frontal fins will move rapidly, and he'll slowly near the top of the tank, but he seems to be very bottom-heavy, and sometimes tips backwards and falls to the bottom of the tank. If his frontal fins aren't moving rapidly, he seems to not even be able to keep afloat. Right now he's resting at the bottom of the tank and swimming a little bit, but it really looks as if he is struggling. Recently, I went back to my house during spring break and had him in a large glass vase (for easy transport and for keeping him while home, without having to move the whole tank. He was fine at my house, during transport and seemed to be fine yesterday. I'm fairly sure he was not injured when I returned him to his tank, as the transfer process was very easy. He seems more melancholy then normal, and spends a lot of time in his hiding-skull, laying at the bottom of it, than he normally does.
His struggle to swim upwards and how he keeps falling is really worrying me. I'm at college in a small town and have no place to take him for care if there is a problem. He never seemed to have any trouble before today! Any tips or suggestions? :(
Also, he tends to "sit" ... His body is vertical, and his tail is curled to the side and against the ground... Is this uh, normal?