Here in Australia I do 30% water changes and have done for a long time on a weekly basis.Fortunately my tap water is around 23 degrees celcius so when mixed with the tank water only brings it down to 25 usually runnig a stable 26.Somedays my water temp will hit 28 degrees due to very hot days here in Qld.I use Prime by Seachem as it only needs 5 ml per 200 L.I pour it straight in the tank and don't prepare the water 24 hrs in advance like other members do,however I put enough dechlorinator in for the whole tank volume and not just the water being replaced.I have never had any problems in any of my tanks other than a case of ich from a newly introduced fish.Now I have a quarrantine tank and have never had ich in any other tank since.
Also make sure your product also removes Chloramines which is put in the water to preserve chlorine.