Although I did turn off the filter, the bacteria from aquarium decor should have flourished by this time, right? I just checked and ammonia is 0, and nitrite is 0. I use API's drops and color comparison to a chart to test it.
For water change, I first fill the water in a bucket and add stress coat and keep it until my next water change. I take about 1 gallon or so at a time and heat it on my stove top to the right temp and pour it into the tank which has been siphoned and cleaned of 25% or so of its water. Not sure what you mean by how do acclimate after. The conditions are per-acclimatized for the water based on the tank conditions.
Not sure about the color of his poop :(; also not sure about the black worms in my new water, I filled it about a week earlier and when I was about to do my water change, I saw them. They were hanging down in the bottom of the bucket. I used abut 1 gallon from the top layer (had to :()... I threw them away, cleaned the bucket with hot water and refilled water.
Not sure if he is gasping.. but when he lay under water for about 48 hours, his gill was opening and closing. Maybe a slight redness to his gills..but he is blue and red and it is difficult to say for sure.
I have epsom, I'll try that- thanks!
He is my only fish and the only tank resident. I dont have a spare tank (i have a bowl, but I don't ever take him out of his tank- that would stress him out).
Should I use all those antibiotics?

Will water change by itself take care of the illness?
I just changed his water on Sunday, when should I change it next?
I will go to the pet store tomorrow, please let me know which medication (or not) to use.