That size of a tank most opt not to use a filter as they can sometimes be too strong for the male- if you keep a filter in it then 2 50%s, 1 water only and 1 with vacuuming or stir/dip to remove waste/debris out of the substrate.
If you remove the filter you will want 1 50% and 1 100% per week water change.
Regardless of size and filter, you will always need to do a water change per week.
As mentioned above, no reason to use medication- that right there can be irritating him and his gills, along with an ammonia build up after 2 weeks of no water change.
Just a good water conditioner is all that is needed.