your tank seems a little small. You could get a 5 gal critter keeper for about $13 at amazon or 3 gal at petco for $12.
with a tank that small you may have to do more water changes.
by betta pellets do you mean a random betta food from the petstore? you may want to switch to new life spectrum or omega brand. bad quality food can lead to constipation and swim bladder disease.
also you should feed your betta more and space them out. I feed mine 5 pellets a day. 2 in the morning, 1 in the afternoon and 2 before i go to bed. feeding him all at once can lead to constipation, swim bladders disease and pineconing.
the does the goatee look like fungus? sounds like cotton mouth. internet says that the causes can be stressed by conditions such as poor water quality
, inadequate diet, or stress from handling and shipping.
suggested treatment is
- Change water
- Vacuum gravel
- Add aquarium salt
- Treat with copper sulfate or antibiotic
- Discontinue carbon filtration during treatment
i don't have any experience with cottonmouth so I suggest you wait for some other forum member to comment before you start medication. but do the water change and add some aquarium salt. its suggested to do 1 tbsp per 5 gal