My Betta Thai became sick while I was away on vacation I did a water change a week before. and a full water change as soon as I noticed his tail fins deteriorating. I'm not sure what happened but here is the info about him.
What size is your tank? 3.5gallons
What temperature is your tank? 78 degrees farenheit
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? 2 1" cory catfish
What type of food do you feed your betta fish? hikari betta pellets
How often do you feed your betta fish? 2 times daily
How often do you perform a water change? 3-4 weeks
What percentage of the water do you change when you perform a water change? 50%
What type of additives do you add to the water when you perform a water change? Aquarium Salt
Have you tested your water? If so, what are the following parameters?
Nitrate: 0 ppm
Hardness: didn't test
Alkalinity: didn't test
Symptoms and Treatment
How has your betta fish's appearance changed? fins and tail rot visible, clumping fins
How has your betta fish's behavior changed? lethargic, on 1/3 he would eat but only if I crushed the pellets. today (1/4) he is not eating and hanging around the filter very still mostly.
When did you start noticing the symptoms? Monday. 1/2
Have you started treating your fish? If so, how? Started today (1/4) with Maracyn-Two
Does your fish have any history of being ill? no
How old is your fish (approximately)? got him ~2.5 months ago.
attached is a picture now and when i first got him. please help I don't know what else to do. If i lower the water level my filter won't work and I read I should keep filtration going when treating with medicine.