Sick betta - pale, lethargic, not eating

[Cos]

hello, I'm new to the site and new to keeping fish. I have a small tank, with 1 betta (Bertie), 1 neon tetra and 1 Sterbas Cory catfish. Bertie was fine until a week ago (eating well, swimming about, curious), but now sits in the top corner of the tank head up, not eating at all and is looking really pale. I thought I could see white patches, so I'm treated for fungal infection at the moment. Any advice would be much appreciated, thank you!

Housing
What size is your tank? 2 galllon
What temperature is your tank? ~80 deg
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? yes
Is your tank heated? yes
What tank mates does your betta fish live with? 1 neon tetra and 1 sterbai cory

Food
What type of food do you feed your betta fish? mixture oftropical pellets, and dried blood worms and brine shrimp
How often do you feed your betta fish? every day

Maintenance
How often do you perform a water change? once a week
What percentage of the water do you change when you perform a water change? about 20%
What type of additives do you add to the water when you perform a water change? Aquasafe water treatment

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: NA
Nitrite: 0 ppm
Nitrate: 20 ppm
pH: 8.5
Hardness: 180 ppm (carbonate hardness 240 ppm)
Alkalinity: NA


Symptoms and Treatment
How has your betta fish's appearance changed? he's gone pale and grey
How has your betta fish's behavior changed? lethargic, not interested in anything
When did you start noticing the symptoms? about 1 week ago
Have you started treating your fish? If so, how? yes, anti fungal treatment and aquarium salt
Does your fish have any history of being ill? No
How old is your fish (approximately)? I've had hime for a few months, but not sure how he was from the pet store

[Oldfishlady]

Welcome to the forum and sorry you are having problems.....sadly, 2gal is not big enough for other fish along with the Betta.....

Due to overcrowding and poor water quality...the fish are stressed and in turn can compromise the immune response.......

In a 2gal filtered tank with just the Betta...no other fish....twice weekly 50% water changes are needed to maintain water quality....

Right now-I would re-home the other species of fish or get a larger tank of at least 10gal....both the corydora and neon are schooling fish and do much better when kept in a proper school of their own species and both can also be sensitive to medication and salt.....I would start making 50% daily water changes for them in the 2g for now with like temp dechlorinated water....

Qt the Betta in a small container and start-50% daily water changes for a few days then 100% and see if he clear up...if not, I would start him on a salt treatment 1tsp/gal for 10 days along with 100% daily water changes.....

Keep us posted....

[Cos]

Thanks for all your advice, it was very helpful.

I'm doing frequent 50% water changes, with salt added now, and did 100% change as well. My plan is to buy a much bigger tank for schooling fish, and until that arrives I'll be continuing with frequent changes.

My betta is doing much better, active, eating, better colour, which is a huge relief!