Betta sick, not sure what has

Question
I have a young double tail. I've had him for a few months but last night when I got home he was acting funny.

At first I thought he might have fin rot because they looked a little ragged but its hard to tell with his coloring. I added aquarium salt and 1/4 teaspoon melafix to his 2.5 gallon unfiltered aquarium.

He gets 1-2 50% water changes a week, and since it is summer and his tank is small there is no heater. av temp 78-85, my other bettas seem to be fine. Mostly it stays around the 80s

BUT he is swimming funny, rigidly and holding his tail more stiffly but not clamped. He floats near top and bottom of tank, but still gets active when someone comes by him. my BF said he looked a little bloated so I stopped feeding him last night. the one pellet I had put in before I noticed the bloat he kept going after and spitting out before not eating it. He also looks very pale.

Does he have bloat too? He's not swelling like dropsy. I've never had a betta swim like that before. The Melafix seems to have perked him up a little, he was more lively this morning but it hurts to watch him swim.

EXTRA info: he gets 3 betta bits twice a day (this is what the directions said) have a small bamboo plant in his tank (live) and just enough gravel to cover the ground. My other tank is a cycled 10 gal with two sister bettas and 2 cories, they are all fine (no heater)

Answer
Ashley,
Melafix, if not used properly, can be fetal for a Betta. You use 5 ml for 10 gallons of water which breaks down to .5 per gallon. If he is only in a 2.5 gallon, then you should only use 1 ml. Be very care when using this medication. If he is bloated, feed him a cooked shelled pea cut into very small pieces. This should help with the swim bladder disease. A Betta's stomach is the size of his eye. Over feeding them can bring this on. Feed him 2 pellets a day. Going without a heater is ok for the summer but it is best for them to have one at all times. The fluctuation in temperature from day to night is not good. They need to have a steady temp at all times. Do a 25% water change now and do not add any medication at this time. You can try him in a salt water bath. This should help him as well. After you feed him the pea, fast him for 2 days to let the pea do its job. Let me know if you need help with the bath.