Try to keep ball park amount of the water you take out with water changesin mind, and replace the dose of meds back to make up for the water with meds removed.
Meds and salt all work on the same principal, ....it is.that the the osmotic pressure they produce is too much for the young ick that hatch off the fish to tolerate. Each spot releases up to 100 new young ick, and it is at that stage they are vulnerable to the osmotic pressure produced by the meds.
The problem with using heat alone, is that their are strains of ick high temps do not kill.
I live in Panama and there is a strain here, that resists water temps in the 90sF, so it is feasible that with imports of fish, new strains of ick are also imported. A strain from New York or Idaho may be killed by heat, but a strain from warm waters in Venezuela or Congo, may not.