Well,it's not cottony like fungus. It looks like poop but it's just staying there.
What size is your tank? 20 gallons
What temperature is your tank? 81 F
Does your tank have a filter?Yes, Tetra whisper 20 (power filter)
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? 4 neon tetras, 1 of which have Neon Tetra Disease, and 1 baby albino bristlenose pleco
What type of food do you feed your betta fish?Omega One pellets, with freeze dried bloodworms, Daphnia or Mysis once a week. She also eats some of the Tetra fish flakes that the Neons get.
How often do you feed your betta fish? Once a day, 2 pellets
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? 2 1/2 gallons, plus evaporation
What type of additives do you add to the water when you perform a water change? Aqueon Water conditioner
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?White blob on her vent, looks like poop, but it's not doing anything. None of the other fish have it.
How has your betta fish's behavior changed? N/A
When did you start noticing the symptoms? A month or two ago
Have you started treating your fish? If so, how? No
Does your fish have any history of being ill? No
How old is your fish (approximately)? I got her 7 months ago from Petco.
Well, after a prolapse is a swelling, Epsom salt might be worth a try- it is recommended here against swellings.
But I am pretty much out of my depth here and would wish someone more knowledgeable could chime in here.
In any case, keep the water clean to prevent infections, do frequent water changes. And if you notice changes, like it gets bigger, or red, or infected (for example with fluffy bacteria) you might have to use antibiotics.
Sadly I do not know a lot about prolapses in fish....
I am sorry I have not been by the forum I was taking finals. I am not sure what the cause is. I would suggest cross posting on the breeder's forum an experienced breeder may have come across before. Post the picture with link to your fish emergencies post so they can easily answer you in the right place. If no one answers you soon you might try getting some Lifeguard from Walmart it treats early generalized disease symptoms I have seen it clear up something that looked like this on another part of a fishes body which is a smooth fungus that grows on the body.
My boy has something similar.. I'm treating him for dropsy as well but epsom salt might be a good thing to try. I've read that prolapses tend to heal themselves and are caused by over feeding but I don't overfeed my boy.
Good luck, I hope she pulls through for you. 1tbs/gallon is the suggested dosage.