The good nitrifying bacteria live in the filter and on the gravel, tank sides etc. Very little good bacteria live in the water. Therefore, water changes properly done will have little effect on Nitrites, Nitrates or Ammonia, other than to lower it.
I had a Bluegill in a 10 gallon tank treating it with Melafix for a wound on its side.
I was doing 100% water changes every day, using properly treated water, of course. I did this on the advice of one of the experts in the
NANFA forum. I did this for a week. Today the fish is fine.
Although I do 25%-30% water changes every week once a month I do a 50% change on my two largest tanks. I'd do a larger change but the barrel I use is only 55 gallons.