I see you saw my Epsom salt post on the other thread.
After the treatment is over, don't worry about removing the Epsom salt all at once. As you do your regular water changes, it'll be removed from the tank.
The general recommendation is to do at least one 50% water change per week on a filtered 5 gal tank. (Per OFL's recommendation thread.)
I would try to do more frequent water changes though while the treatment is going on. This will remove any toxins that the fish may be shedding, or bacteria in the water.
Once the treatment is over, you can do a 50% change. This will take the concentration down to 0.5 tsp/gal immediately. Then, you can do another 50% change several days later, which will drop it to 0.25 tsp/gal. Plus, your plants will be using some of it, as well.