Best water conditioner here in Australia to use is Seachem prime as we have a lot of chlorine n chloramine in our tap water. For water changes I have a 50 gallon drum with a pump, air stone and heater and usually just top it up with water and give it a triple dose of Seachem prime( says you can do 4x safely in emergency) a day or 2 before water change day. I do weekly 70-80% changes and my fish couldn't be happier and I never have health problems. This also ensures my nitrates are always between 0 and 5. I'd be doing 50% daily water changes until everything levels out.