I currently have ick in my tank caused by stress, changing our gravel substrate to sand and adding new fish. I added salt attempted to raise temp, no effect. so I added Ick out sensitive..Formaldehyde 5.55%...because I have catfish and clown loaches. It says after 24 hours do a 50% water change, then for ick repeat every 3 days for 3 treatments. If we do this routine a 50% water change 3 times equals 225 gallons of water changed. Is this necessary or could partial water changes and vacuuming gravel be as effective?