Hi, I recently received a fish through aquabid from Siribetta yesterday. I used Jennifer as a transhipper because she was reputable and came highly recommended. The fish (Milo) arrived pale and with half of his caudal fin chewed off, but otherwise alert and responsive with no visible defects, disease, or injuries. I put him in a 1 gal critter keeper with a 25 watt adjustable Hydor heater set at 83 degrees after acclimating him. He regained most of his color and was voraciously hungry when I fed him. This morning I noticed that he had a HUGE poop in the color of his fins

. It was blue and yellow, which isnt surprising because their poop is supposed to be the color of their food, right? In the last few hours I noticed that he seemed moody or lethargic, he was hiding behind the heater a lot and I can't tell if he was sleeping or if something was wrong. I don't have a water testing kit, so after awhile I just decided to do a 100% water change. I also added a zoomed betta leaf because his tank was empty except the heater. He seems a bit better now, more active but still lying around heater every now and then. Should I be worried? I've attached pictures
Housing
What size is your tank? 1G for now. I plan on moving him to a 2.5 G soon with decor, etc.
What temperature is your tank? 83 Fahrenheit
Does your tank have a filter? No
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
Food
What type of food do you feed your betta fish? NLS betta
How often do you feed your betta fish? 2 times a day, 2-3 pellets each time
Maintenance
How often do you perform a water change? Everyday so far
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? Seachem Prime
Water Parameters:
Have you tested your water? If so, what are the following parameters?
Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:
Symptoms and Treatment
How has your betta fish's appearance changed? He had chewed off half of his caudal fin and part of his dorsal fin when he arrived yesterday. It seems to be healing with no fin rot I can detect
How has your betta fish's behavior changed? Started lying at the bottom of the tank slowly leaning to one side.
When did you start noticing the symptoms? a few hours ago
Have you started treating your fish? If so, how? No
Does your fish have any history of being ill? Not that I am aware
How old is your fish (approximately)? I would say 2-3 months? No idea, really. I got him off of aquabid and his body without the fins is probably an inch long.. he's definitely smaller than my other two bettas that are 5 months and undetermined.